ACCEPTCAT Catalog
This table, the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT)
Catalog, contains the radial entropy profiles of the intracluster medium
(ICM) for a collection of 239 clusters taken from the Chandra X-ray
Observatory's Data Archive. Entropy is of great interest because it controls
ICM global properties and records the thermal history of a cluster. The
authors find that most ICM entropy profiles are well fitted by a model which
is a power law at large radii and approaches a constant value at small radii:
K(r) = K0 + K100 (r/100 kpc)alpha, where K0 quantifies the typical
excess of core entropy above the best-fitting power law found at larger
radii. The authors also show that the K0 distributions of both the full
archival sample and the primary Highest X-Ray Flux Galaxy Cluster Sample
of Reiprich (2001, Ph.D. thesis) are bimodal with a distinct gap between K0
~ 30 - 50 keV cm2 and population peaks at K0 ~ 15 keV cm2 and K0 ~
150 keV cm2. The effects of point-spread function smearing and angular
resolution on best-fit K0 values are investigated using mock Chandra
observations and degraded entropy profiles, respectively. The authors find
that neither of these effects is sufficient to explain the entropy-profile
flattening they measure at small radii. The influence of profile curvature
and the number of radial bins on the best-fit K0 is also considered, and
they find no indication that K0 is significantly impacted by either.
All data and results associated with this work are publicly available via the
project web site http://www.pa.msu.edu/astro/MC2/accept/.
The sample is collected from observations taken with the Chandra X-ray
Observatory and which were publicly available in the CDA (Chandra Data
Archive) as of 2008 August.
AEGISX Catalog
This table contains the X-ray sources detected in the AEGIS-X survey, a
series of deep Chandra ACIS-I observations of the Extended Groth Strip (EGS).
The survey comprises pointings at eight separate positions, each with nominal
exposure of 200 ks, covering a total area of approximately 0.67 deg2 in a
strip of length 2 degrees. In their paper, the authors describe in detail an
updated version of the data reduction and point-source-detection algorithms
used to analyze these data. A total of 1325 band-merged sources have been
found to a Poisson probability limit of 4 x 10-6, with limiting fluxes of
5.3 x 10-17 erg cm-2 s-1 in the soft (0.5 - 2 keV) band and 3.8 x
10-16 erg cm-2 s-1 in the hard (2 - 10 keV) band. They present
simulations verifying the validity of their source-detection procedure and
showing a very small, <1.5%, contamination rate from spurious sources.
Optical/NIR counterparts have been identified from the DEEP2, CFHTLS, and
Spitzer/Infrared Array Camera (IRAC) surveys of the same region. Using a
likelihood ratio method, they find optical counterparts for 76% of their
sources, complete to RAB = 24.1, and, of the 66% of the sources that have
IRAC coverage, 94% have a counterpart to a limit of 0.9 uJy at 3.6 um (mAB
= 23.8). After accounting for (small) positional offsets in the eight Chandra
fields, the astrometric accuracy of Chandra positions is found to be 0.8
arcseconds rms; however, this number depends both on the off-axis angle and
the number of detected counts for a given source.
AEGISXDCXO Catalog
This table is based on the results of deep Chandra imaging of the central
region of the Extended Groth Strip, the AEGIS-X Deep (AEGIS-XD) survey. When
combined with previous Chandra observations of a wider area of the strip,
AEGIS-X Wide (AEGIS-XW), these provide data to a nominal exposure depth of
800ks in the three central ACIS-I fields, a region of approximately 0.29
deg2. This is currently the third deepest X-ray survey in existence; a
factor ~2-3 shallower than the Chandra Deep Fields (CDFs), but over an area
~3 times greater than each CDF. This table contains a catalog of 937 point
sources detected in the deep Chandra observations, along with identifications
of the X-ray sources from deep ground-based, Spitzer, GALEX, and Hubble Space
Telescope imaging. Using a likelihood ratio analysis, the authors associate
multiband counterparts for 929/937 of their X-ray sources, with an estimated
95% reliability,making the identification completeness approximately 94% in a
statistical sense. Reliable spectroscopic redshifts for 353 of the X-ray
sources are available predominantly from Keck (DEEP2/3) and MMT Hectospec, so
the current spectroscopic completeness is ~38%. For the remainder of the
X-ray sources, the authors compute photometric redshifts based on multiband
photometry in up to 35 bands from the UV to mid-IR. Particular attention is
given to the fact that the vast majority of the X-ray sources are active
galactic nuclei and require hybrid templates. The photometric redshifts have
a mean accuracy sigma = 0.04 and an outlier fraction of approximately 5%,
reaching sigma = 0.03 with less than 4% outliers in the area covered by
CANDELS.
The new AEGIS-XD Chandra data were taken at three nominal pointing positions,
which the authors have designated AEGIS-1, AEGIS-2, and AEGIS-3. These
observations were all taken in the time period 2007 December 11 to 2009 June
26 using the ACIS-I instrument. The centers of the 3 AEGIS fields correspond
fairly closely to those of the EGS-3, EGS-4, and EGS-5 fields of Laird et al.
(2009, ApJS, 180, 102).
The Rainbow Cosmological Surveys Database
(http://rainbowx.fis.ucm.es/Rainbow_Database/Home.html; see Section 4 of the
reference paper for more details) contains many multiwavelength photometric
datasets giving information on optical and infrared sources in these fields.
The characteristics of these datasets are given in Table 7 of the reference
paper.
AKNEPDFCXO Catalog
This table contains results from the 300-ks Chandra survey in the AKARI North
Ecliptic Pole (NEP) deep field. This field has a unique set of 9-band
infrared photometry covering 2-24 micron from the AKARI Infrared Camera,
including mid-infrared (MIR) bands not covered by Spitzer. The survey is one
of the deepest ever achieved at ~15 micron, and is by far the widest among
those with similar depths in the MIR. This makes this field unique for the
MIR-selection of AGN at z ~1. The authors have designed a source detection
procedure, which performs joint Maximum Likelihood PSF fits on all of their
15 mosaicked Chandra pointings covering an area of 0.34 square degrees. The
procedure has been highly optimized and tested by simulations. A point source
catalog with photometry and Bayesian-based 90%-confidence upper limits in the
0.5-7, 0.5-2, 2-7, 2-4, and 4-7 keV bands has been produced. The catalog
contains 457 X-ray sources and the spurious fraction is estimated to be
~1.7%. Sensitivity and 90%-confidence upper flux limits maps in all bands are
provided as well.
In their study, the authors searched for optical MIR counterparts in the
central 0.25 square degrees, where deep Subaru Suprime-Cam multi-band images
exist. Among the 377 X-ray sources detected therein, ~80% have optical
counterparts and ~60% also have AKARI mid-IR counterparts. The authors
cross-matched their X-ray sources with MIR-selected AGN from Hanami et al.
(2012, PASJ, 64, 70). Around 30% of all AGN that have MID-IR SEDs purely
explainable by AGN activity are strong Compton-thick AGN candidates.
The source catalog contained in this table uses an internal threshold of ML =
9.5 which corresponds to MLempir ~12 (see Sect. 4.3.3 of the reference
paper for more details). In total, 457 sources are detected, of which 377
objects fall in the deep Subaru imaging region (shown in Figure 1 of the
reference paper). This catalog is designed to identify X-ray emitting objects
in the Chandra/AKARI NEP deep field. Together with the optimized
cross-identification procedure, the clear advantage of the catalog is the
very high reliability, while the catalog sacrifices completeness for objects
with low counts (see Figure 9 in the paper). Only ~1.7% of the objects listed
in the source catalog are expected to be spurious source detections.
The two sources that have an ML-threshold in the 0.5-7 keV band below 9.5
originate from a 0.5-7 keV single-band source detection run. To quote similar
ML values for all objects, the authors list the total 0.5-7 keV ML values
from the joint 3-energy band source detection run. The listed counts, count
rates, fluxes, and the corresponding uncertainties in the 0.5-7 keV band are
taken from the single-band detection run.
Considering the uncertainty in the astrometric calibration, all sources
should be considered as possible X-ray counterparts that are within a radius
of rmatch = sqrt(sigmatotal2+sigmaastro2), with sigmatotal = 5 *
sqrt(sigmasys2+sigmastat2) and sigmasys = 0.1 arcseconds and
sigmaastro = 0.2 arcseconds (astrometric uncertainty).
The authors also created a low-probability source catalog (not contained in
this present HEASARC table): they caution that, due to the significant number
of spurious sources in the low-probability catalog, it should NOT be used to
select X-ray sources or to increase the sample size of X-ray-selected
objects. It can be of interest if the scientific goal requires one to EXCLUDE
potential X-ray emitting objects from a sample with a high completeness,
since, using this strategy, one accepts those objects that are excluded are
not associated with an X-ray-emitting object. The low-probability source
catalog (available at http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/446/911/ as
the files lowpscat.dat.gz and lowpscat.fits) has a lower maximum likelihood
threshold than the main source catalog (an internal threshold of ML = 5,
corresponding to MLempir ~9.5). This catalog contains 626 detected sources,
of which 506 are located within the deep Subaru imaging region. Based on
their simulated data, the authors conclude that 19% of all the
low-probability source catalog entries are false detections. Considering only
the deep Subaru imaging area the spurious source fraction drops to 15%.
When using information from this catalog, please cite the reference paper:
Krumpe et al. (2015, MNRAS, 446, 911).
ARCQUINCXO Catalog
The Galactic centre (GC) provides a unique laboratory for a
detailed examination of the interplay between massive star formation and the
nuclear environment of our Galaxy. Here are presented some of the results from
a 100-ks Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of the
Arches and Quintuplet star clusters in the form of a catalog of 244 point-like
X-ray sources detected in the observation.
The deep Chandra ACIS-I observation (Obs. ID: 4500) was carried out on
2004 June 9. The Arches cluster was placed about 1-arcmin away from
the aim point to minimize the effect of the CCD gaps on mapping the
extended X-ray emission around the cluster.
BMWCHANCAT Catalog
This table contains the BMW-Chandra source catalog drawn from essentially all
Chandra ACIS-I pointed observations with an exposure time in excess of 10 ks
that were public as of March 2003 (136 observations). Using the wavelet
detection algorithm developed by Lazzati et al. (1999ApJ...524..414) and
Campana et al. (1999ApJ...524..423C), which can characterize both point-like
and extended sources, the authors identified 21325 sources. Among them, 16758
are serendipitous, i.e. not associated with the targets of the pointings, and
do not require a non-automated analysis. This makes this catalog the largest
compilation of Chandra sources as of the date of publication of this catalog
(August 2008). The 0.5 - 10 keV absorption corrected fluxes of these sources
range from ~3 x 10-16 to 9 x 10-12 erg/cm2/s with a median of 7 x
10-15 erg/cm2/s.
The catalog consists of count rates and relative errors in three energy bands
(total, 0.5 - 7 keV; soft, 0.5 - 2 keV; and hard, 2 - 7 keV), and source
positions relative to the highest signal-to-noise detection among the three
bands. The wavelet algorithm also provides an estimate of the extension of
the source. The authors include information drawn from the headers of the
original files, as well, and extracted source counts in four additional
energy bands, SB1 (0.5 - 1 keV), SB2 (1 - 2 keV), HB1 (2 - 4 keV), and HB2 (4
- 7 keV). They computed the sky coverage for the full catalog and for a
subset at high Galactic latitude (|b| > 20 degrees). The complete catalog
provides a sky coverage in the soft band (0.5 - 2 keV, S/N = 3) of ~8 deg2
at a limiting flux of 10-13 erg/cm2/s, and ~2 deg2 at a limiting flux of
~10-15 erg/cm2/s. The total numbers of matches with the FIRST, IRASPSC,
2MASS, and GSC2 catalogs obtained after a closest-distance selection are 13,
87, 6700, and 4485, respectively.
CANDELSCXO Catalog
Improving the capabilities of detecting faint X-ray sources is fundamental to
increase the statistics on faint high-z AGN and star-forming galaxies. The
authors performed a simultaneous maximum likelihood point-spread function
(PSF) fit in the 0.5-2 keV and 2-7 keV energy bands of the 4 Ms Chandra Deep
Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected
galaxies. For each detected source, they provide X-ray photometry and optical
counterpart validation. The authors validated this technique by means of a
ray-tracing simulation, and detected a total of 698 X-ray point-sources with
a likelihood L > 4.98 (i.e.> 2.7sigma). They show that the prior knowledge of
a deep sample of Optical-NIR galaxies leads to a significant increase of the
detection of faint (i.e. ~ 10-17 erg s-1 cm-2 in the 0.5-2 keV band)
sources with respect to "blind" X-ray detections. By including previous
catalogs, this work increases the total number of X-ray sources detected in
the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of
extremely faint X-ray sources assembled to date. These results suggest that a
large fraction of the optical counterparts of our X-ray sources determined by
likelihood ratio actually coincides with the priors used for the source
detection. Most of the newly detected sources are likely star-forming
galaxies or faint absorbed AGN. The authors identified a few sources with
putative photometric redshift z > 4. Despite the low number statistics, this
sample significantly increases the number of X-ray selected candidate high-z
AGN.
The 4-Ms CDFS consists of 23 observations described in Table 1 of Luo et al.
(2008, ApJS, 179, 19) plus 31 other pointings described in Xue et al. (2011,
ApJS, 195, 10, hereafter X11) for a total exposure of ~4 Ms. For the purpose
of this paper, the authors employed only observations taken with a focal
temperature of <= -120 C, since at higher temperatures the background cannot
be modeled with their technique.
CARGM31CXO Catalog
Gum 31 is a prominent, but still rather poorly studied, HII region around the
stellar cluster NGC 3324 at the northwestern periphery of the Carina nebula
complex. The aim of the authors aim was to reveal and characterize the young
stellar population in Gum 31. An X-ray survey is the only efficient way to
identify young stars in this region, which has extremely high galactic
field-star contamination, that can avoid the strong biases of
infrared-excess-selected samples of disk-bearing young stars.
The authors used the Chandra observatory to perform a deep (70 ks) X-ray
observation of the Gum 31 region and detected 679 X-ray point sources. This
extends and complements the X-ray survey of the central Carina nebula regions
performed in the Chandra Carina Complex Project (CCCP, available in the
HEASARC database system as the CARINACXO table). Using deep near-infrared
images from their recent VISTA survey of the Carina nebula complex, their
comprehensive Spitzer point-source catalog, and optical archive data, the
authors identify counterparts for 75% of these X-ray sources.
The aimpoint of the ACIS-I observation was set to be RA(J2000) = 10h 37m
36.6s, Dec(J2000) = -58o 41' 18". This position is close to the center of
the H II region, and allows both the stellar cluster NGC 3324 and the cluster
G286.38-0.26 to be in the inner parts of the field-of-view, where the
point-spread function is still very good. The pointing roll angle (i.e., the
orientation of the detector with respect to the celestial north direction)
was 138.35o. The ACIS field-of-view is just wide enough to cover the full
spatial extent of the optically bright Gum 31 H II region and some parts of
the surrounding dust shell (see Fig. 1 of the reference paper). The ACIS-I
field of view is 17' x 17', which corresponds to 11.3 p x 11.3 pc at the Gum
31 distance of 2.3 kpc). The total net exposure time of the observation was
68,909s (19.14 h). The details of the source detection procedures are
described in Section 21. of the reference paper. The final X-ray catalog
contains 679 individual point sources. The number of extracted counts ranges
from 3 for the faintest sources, up to 920 for the strongest source, while
the median value is 11 counts.
This table contains the basic X-ray properties and near- and mid-infrared
photometry of the X-ray sources detected in the Gum 31 field. The details of
the IR matching to the X-ray sources are given in Sections 4.1, 4.2 and 4.3
of the reference paper.
CARINACLAS Catalog
The Chandra Carina Complex Project (CCCP) provides a sensitive X-ray survey
of a nearby starburst region over > 1 deg2 in extent. Thousands of faint
X-ray sources are found, many concentrated into rich young stellar clusters.
However, significant contamination from unrelated Galactic and extragalactic
sources is present in the X-ray catalog. In their paper, the authors describe
the use of a naive Bayes classifier to assign membership probabilities to
individual sources, based on source location, X-ray properties, and
visual/infrared properties. For the particular membership decision rule
adopted, 75% of CCCP sources are classified as members, 11% are classified as
contaminants, and 14% remain unclassified. The resulting sample of stars
likely to be Carina members is used in several other studies, which appear in
the special issue of Astrophysical Journal Supplement (Volume 194, May 2011
Issue) which was devoted to the CCCP.
CARINACXO Catalog
This database table contains a catalog of >~ 14,000 X-ray sources observed by
the ACIS instrument on the Chandra X-ray Observatory within a 1.42 deg2
survey of the Great Nebula in Carina, known as the Chandra Carina Complex
Project (CCCP). The study from which this table is taken appeared in a
special ApJS issue which was devoted to the CCCP. In it, the authors
described the data reduction and analysis procedures performed on the X-ray
observations, including calibration and cleaning of the X-ray event data,
point-source detection, and source extraction. The catalog appears to be
complete across most of the field to an absorption-corrected total-band
luminosity of ~ 1030.7 erg s-1 for a typical low-mass pre-main-sequence
star. Counterparts to the X-ray sources were identified in a variety of
visual, near-infrared, and mid-infrared surveys. The X-ray and infrared
source properties presented herein form the basis of many CCCP studies of the
young stellar populations in Carina.
The prefixes 'fb', 'sb' and 'hb' on the names of photometric quantities
designate the full or total (0.5-8 keV), soft (0.5-2 keV), and hard (2-8 keV)
energy bands. Source significance quantities (fb_prob_no_src, sb_prob_no_src,
hb_prob_no_src, prob_no_src_min) were computed using a subset of each
source's extractions chosen to maximize significance (Broos et al. 2010, ApJ,
714, 1582, hereafter B10, Section 6.2). X-ray source position quantities (RA,
Dec, error_radius) were computed using a subset of each source's extractions
chosen to minimize the position uncertainty (B10, Sections 6.2 and 7.1). All
other quantities were computed using a subset of each source's extractions
chosen to balance the conflicting goals of minimizing photometric uncertainty
and of avoiding photometric bias (B10, Sections 6.2 and 7).
A summary of the counterpart catalogs that were correlated with the Chandra
Carina sources is given in Table 5 of the reference paper and is listed below:
Catalog Scope Reference
Skiff Visual spectral types Skiff (2009, VizieR Online Data Catalog, 1, 2023)
KR Visual photometry Kharchenko & Roeser (2009, VizieR Online Data Catalog, 1280, 0)
PPMXL CCD proper motions (PMs) Roeser et al. (2010, AJ, 139, 2440)
UCAC3 CCD PMs Zacharias et al. (2004, AJ, 127, 3043)
BSS Bright star PMs Urban et al. (2004, VizieR Online Data Catalog, 1294, 0)
CMD Photographic PMs, Tr 14, Tr 16, Cr 232 Cudworth et al. (1993, AJ, 105, 1822)
DETWC Visual photometry, Tr 14 & 16 DeGioia-Eastwood et al. (2001, ApJ, 549, 578)
MDW Visual spectral types, Cr 228 Massey et al. (2001, AJ, 121, 1050)
MJ Visual photometry, Tr 14 & 16 Massey & Johnson (1993, AJ, 105, 980)
CP High-mass photometry, Cr 228 Carraro & Patat (2001, A&A, 379, 136)
DAY Low-mass photometry, Cr 228 Delgado et al. (2007, A&A, 467, 1397)
HAWK-I Deep near-infrared photometry Preibisch et al. (2011, ApJS, 194, 10, CCCP HAWK-I Paper)
2MASS Shallow near-infrared photometry Skrutskie et al. (2006, AJ, 131, 1163)
SOFI Deep near-infrared photometry, Tr 14 Ascenso et al. (2007, A&A, 476, 199)
NACO Deep near-infrared photometry, Tr 14 Ascenso et al. (2007, A&A, 476, 199)
Sana Deep near-infrared photometry, Tr 14 Sana et al. (2010, A&A, 515, A26)
SpVela Mid-infrared photometry (Spitzer) Povich et al. (2011, ApJS, 194, 14, CCCP IR YSOs Paper)
SpSmith Mid-infrared photometry (Spitzer) Smith et al. (2010, MNRAS, 406, 952)
AC ACIS observation of Tr 16 Albacete-Colombo et al. (2008, A&A, 490, 1055)
CBFGRXECXO Catalog
Apparently diffuse X-ray emission has been known to exist along the central
quarter of the Galactic Plane since the beginning of X-ray astronomy; this is
referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray
observations have shown that numerous X-ray point sources account for a large
fraction of the GRXE in the hard band (2 - 8 keV). However, the nature of
these sources is poorly understood. Using the deepest X-ray observations made
in the Chandra bulge field, the authors present the result of a coherent
photometric and spectroscopic analysis of individual X-ray point sources for
the purpose of constraining their nature and deriving their fractional
contributions to the hard-band continuum and Fe K line emission of the GRXE.
Based on the X-ray color-color diagram, they divided the point sources into
three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked
spectrum). The group A sources are further decomposed spectrally into thermal
and non-thermal sources with different fractions in different flux ranges.
From their X-ray properties, the authors speculate that the group A
non-thermal sources are mostly active galactic nuclei and the thermal sources
are mostly white dwarf (WD) binaries such as magnetic and non-magnetic
cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group
B and C sources are X-ray active stars in flares and quiescence,
respectively. In the log N - log S curve of the 2 - 8 keV band, the group A
non-thermal sources are dominant above ~10-14 erg/cm2/s, which is
gradually taken over by Galactic sources in the fainter flux ranges. The Fe
K-alpha emission is mostly from the group A thermal (WD binaries) and the
group B (X-ray active stars) sources.
The authors retrieved 10 archived data sets of the Chandra bulge field (CBF)
taken with the Advanced CCD Imaging Spectrometer-I (ACIS-I; 0.5 - 8.0 keV
energy band with a spectral resolution of ~280 eV for the full width at
half-maximum at 5.9keV) array on board Chandra. The observations were carried
out from 2008 May to August with a total exposure time of ~900 ks.
The authors first extracted point-source candidates using the wavdetect
algorithm in the CIAO package. They set the significance threshold at 2.5 x
10-5, implying that one false positive detection would be expected at every
4 x 104 trials. As a result, 2596 source candidates were found. The number
of their source candidates is nearly the same as that found by Revnivtsev et
al.(2009, A&A, 507, 1211) in the same region. To select significant point
sources from the candidates, the authors examined their validity based on
their photometric significance (PS) and the probability of no source (PB).
The PS is defined as the background-subtracted source counts (Cnet) divided
by its background counts normalized by the area. PB is the probability that
the source is attributable to a background fluctuation, assuming Poisson
statistics. The authors recognized a source to be valid if it satisfied both
these criteria: PS >= 1.0 and PB <= 1.0 x 10-2. As a result, they
obtained 2002 valid point sources.
CCOSMOSCAT Catalog
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that
has imaged the central 0.5 deg2 of the COSMOS field (centered at RA, Dec of
10 hours , +02 degrees) with an effective exposure of ~ 160 ks, and an outer
0.4 deg2 area with an effective exposure of ~ 80 ks. The limiting source
detection depths are 1.9 x 10-16 erg cm-2 s-1 in the soft (0.5 - 2 keV)
band, 7.3 x 10-16 erg cm-2 s-1 in the hard (2 - 10 keV) band, and
5.7 x 10-16 erg cm-2 s-1 in the full (0.5 - 10 keV) band. In this
paper, the authors describe the strategy, design, and execution of the
C-COSMOS survey, and present the catalog of 1761 point sources detected at
a probability of being spurious of < 2 x 10-5 (1655 in the full, 1340 in
the soft, and 1017 in the hard bands). By using a grid of 36 heavily (~ 50%)
overlapping pointing positions with the ACIS-I imager, a remarkably uniform
(+/-12%) exposure across the inner 0.5 deg2 field was obtained, leading to
a sharply defined lower flux limit. The widely different point-spread
functions obtained in each exposure at each point in the field required a
novel source detection method, because of the overlapping tiling strategy,
which is described in a companion paper. This method produced reliable sources
down to a 7-12 counts, as verified by the resulting log N-log S curve, with
sub-arcsecond positions, enabling optical and infrared identifications of
virtually all sources, as reported in a second companion paper.
Supporting data products for this table (including images, event files, and
exposure maps) are available at the
COSMOS Survey website and at
IRSA. At the IRSA website, it
is also possible to search a database that includes "postage stamps" of
the X-ray data for each source, along with the multi-wavelength optical and
infrared data, including the I-band, K-band, and Spitzer 3.6-micron (Band 1)
images used in the Part III paper (Civano et al. 2012) to identify the
sources.
See also the related table CCOSMOSOID for the optical and
infrared identifications of the surveyed X-ray point sources.
CCOSMOSOID Catalog
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8-Ms, Chandra program that
has imaged the central 0.9 deg2 of the COSMOS field down to limiting depths
of 1.9 x 10-16 erg/cm2/s in the soft (0.5-2 keV) band, 7.3 x 10-16
erg/cm2/s in the hard (2-10 keV) band, and 5.7 x 10-16 erg/cm2/s in the
full (0.5-10 keV) band. In this Paper III of the series of papers on this
survey, the authors report the i, K, and 3.6-um identifications of the 1761
X-ray point sources. They use the likelihood ratio technique to derive the
association of optical/infrared counterparts for 97% of the X-ray sources.
For most of the remaining 3%, the presence of multiple counterparts or the
faintness of the possible counterpart prevented a unique association. For
only 10 X-ray sources, they were not able to associate a counterpart, mostly
due to the presence of a very bright field source close by. Only two sources
are truly empty fields. The full catalog, including spectroscopic and
photometric redshifts and classification described here in detail, is
available herein.
See also the related table CCOSMOSCAT for the the surveyed
X-ray point sources.
CCOSMPHOTZ Catalog
In their paper, the authors release accurate photometric redshifts
for 1692 counterparts to Chandra sources in the central square degree of the
Cosmic Evolution Survey (COSMOS) field. The availability of a large training
set of spectroscopic redshifts that extends to faint magnitudes enabled
photometric redshifts comparable to the highest quality results presently
available for normal galaxies. The authors demonstrate that morphologically
extended, faint X-ray sources without optical variability are more accurately
described by a library of normal galaxies (corrected for emission lines) than
by active galactic nucleus (AGN) dominated templates, even if these sources
have AGNlike X-ray luminosities. Preselecting the library on the bases of the
source properties allowed them to reach an accuracy sigma[Delta-z/(1+Zspec)]
~ 0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS
sample. In addition, in this study the authors released revised photometric
redshifts for the 1735 optical counterparts of the XMM-detected sources over
the entire 2 deg2 of COSMOS (these sources are listed in the HEASARC table
XMMCPHOTZ). For 248 sources, their updated photometric redshift differs from
the previous release by Delta-z > 0.2. These changes are predominantly due to
the inclusion of newly available deep H-band^ photometry (HAB = 24 mag). The
authors illustrate once again the importance of a spectroscopic training sample
and how an assumption about the nature of a source together, with the number
and the depth of the available bands, influences the accuracy of the
photometric redshifts determined for AGN. These considerations should be kept
in mind when defining the observational strategies of upcoming large surveys
targeting AGNs, such as eROSITA at X-ray energies and the Australian Square
Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band.
This table contains the photometric redshifts and related quantities for 1694
(note that there appears to be 2 more sources than the above-quoted abstract
states) Chandra sources in the central square degree of the COSMOS field.
Notice that in the original as-published paper no positional information was
provided. The HEASARC has assumed that the source numbers used in the present
catalog are in the same source numbering scheme as used by Elvis et al.
(2009, ApJS, 184, 158, the Chandra COSMOS Survey Point Source Catalog,
available at the HEASARC as the CCOSMOSCAT table) and thus obtained the
positions and (position-based) names corresponding to these sources.
CCOSRSSFAG Catalog
X-ray surveys contain sizable numbers of star-forming galaxies, beyond the
AGN which usually make up the majority of detections. Many methods to
separate the two populations are used in the literature, based on X-ray and
multi-wavelength properties. The authors aim at a detailed test of the
classification schemes and to study the X-ray properties of the resulting
samples. They build on a sample of galaxies selected at 1.4 GHz in the
VLA-COSMOS survey, classified by Smolcic et al. (2008, ApJS, 177, 14)
according to their optical colors and also observed by Chandra. A similarly
selected control sample of AGN is also used for comparison. The authors
review some X-ray based classification criteria and check how they affect the
sample composition. The efficiency of the classification scheme devised by
Smolcic et al. (2008) is such that ~30% of composite/misclassified objects
are expected because of the higher X-ray brightness of AGN with respect to
galaxies. The latter fraction is actually 50% in the X-ray detected sources,
while it is expected to be much lower among X-ray undetected sources. Indeed,
the analysis of the stacked spectrum of undetected sources shows,
consistently, strongly different properties between the AGN and galaxy
samples. X-ray based selection criteria are then used to refine both samples.
The radio/X-ray luminosity correlation for star-forming (SF) galaxies is
found to hold with the same X-ray/radio ratio valid for nearby galaxies. Some
evolution of the ratio may be possible for sources at high redshift or high
luminosity, though it is likely explained by a bias arising from the radio
selection. Finally, in their paper the authors discuss the X-ray number
counts of star-forming galaxies from the VLA- and C-COSMOS surveys according
to different selection criteria, and compare them to the similar
determination from the Chandra Deep Fields. The classification scheme
proposed here may find application in future works and surveys.
This table contains the catalogs of radio-selected SF- and AGN-candidate
sources with an X-ray detection in C-COSMOS which were contained in Tables 2
and 3 of the reference paper, respectively. The HEASARC has merged these into
a single table, adding a new parameter sample which is set to 'SFG' for
radio-selected SF-candidate sources from Table 2 and to 'AGN' for the
AGN-candidate sources from Table 3.
CDFN2MSNEW Catalog
This table contains the improved point-source catalog for the 2-Ms Chandra
Deep Field-North (CDF-N) Survey, implementing a number of recent improvements
in Chandra source-cataloguing methodology. For the CDF-N, the main catalog
(entries from which are indicated with parameter values of source_sample =
"Main" in this HEASARC representation) contains 683 X-ray sources detected
with wavdetect at a false-positive probability threshold of 10-5 that also
satisfy a binomial-probability source-selection criterion of P <= 0.004. Such
an approach maximizes the number of reliable sources detected: a total of 196
main-catalog sources are new compared to the Alexander et al. (2003, AJ, 126,
539) CDF-N main catalog. The authors also provide a CDF-N supplementary
catalog that consist of 72 sources (entries from which are indicated with
parameter values of source_sample = "Supp" in this HEASARC representation)
detected at the same wavdetect threshold and having P of 0.004-0.1 and Ks
<= 22.9 mag counterparts. For all 755 CDF-N sources, including the 234 newly
detected ones (these being generally fainter and more obscured), the authors
determine X-ray source positions utilizing centroid and matched-filter
techniques; they also provide multi-wavelength identifications, apparent
magnitudes of counterparts, spectroscopic and/or photometric redshifts, basic
source classifications, and estimates of observed active galactic nucleus and
galaxy source densities around respective field centers. Simulations show
that the CDF-N main catalog is highly reliable and reasonably complete.
Background and sensitivity analyses indicate that the on-axis mean flux
limits reached represent a factor of ~1.5-2.0 improvement over the previous
CDF-N limit.
The 2 Ms CDF-N consists of a total of 20 separate Chandra observations taken
between 1999 November 13 and 2002 February 22 with ACIS (see Alexander et
al., 2003, AJ, 126, 539 for more details).
CDFN2MSOI2 Catalog
This table contains the redshift catalog for the X-ray sources detected in
the Chandra Deep Field-North (CDF-N). The catalog for the CDF-N includes
redshifts from previous work. The authors have extended the redshift
information for the full sample using photometric redshifts. The goal of the
OPTX Project is to use this survey, together with the Chandra Large-Area
Synoptic X-Ray Survey (CLASXS) and the Chandra Lockman Area North Survey
(CLANS), which are among the most spectroscopically complete surveys to date,
to analyze the effect of spectral type on the shape and evolution of the
X-ray luminosity functions and to compare the optical spectral types with the
X-ray spectral properties. The CLANS and CLASXS surveys bridge the gap
between the ultra-deep pencil-beam surveys, such as the Chandra Deep Fields,
and the shallower, very large-area surveys.
This table also contains updated optical and infrared photometric data for
the X-ray sources in the CDF-N. Typical photometric uncertainties are given
in Section 3.6 of the reference paper (Trouille et al. 2008).
The X-ray information for the sources detected in the CDF-N 2-megasecond
exposure which was published in Alexander et al. (2003, AJ, 126, 539) is
available as the HEASARC CHANDFN2MS table, while the earlier catalog which
listed information about optical and infrared counterparts (Barger et al.
2003, AJ, 126, 632) is available as the HEASARC CDFN2MSOID table.
CDFN2MSOID Catalog
The Chandra Deep Field North (CDFN) 2-Megasecond (2Ms) Optical and IR Catalog
is an optical and near-infrared catalog for the X-ray sources in the 2Ms
Chandra observation of the Hubble Deep Field North region. It has
high-quality multicolor imaging data for all 503 X-ray point sources in the
X-ray-selected catalog and reliable spectroscopic redshifts for 284. The
authors have spectroscopically identified six high-redshift (z > 1) type II
quasars (L2-8keV > 1044 ergs/s) in their
sample. The spectroscopic completeness for the R <= 24 sources is 87%. The
spectroscopic redshift distribution shows two broad redshift spikes
that have clearly grown over those originally seen in the 1Ms
exposure. The spectroscopically identified extragalactic sources
already comprise 75% of the measured 2-8 keV light. Redshift slices
versus 2-8 keV flux show that an impressive 54% of the measured 2-8 keV
light arises from sources at z < 1 and 68% from sources at z < 2.
The X-ray sample is presented in Alexander et al. (2003, AJ, 126, 539,
hereafter ABB2003) and in CDS Catalog <J/AJ/126/539>, and is also available
in the HEASARC Browse system as the CHANDFN2MS table. The optical imaging
data consist of Johnson B, Johnson V, Cousins R, Cousins I, and Sloan z'
observations obtained with the Subaru prime-focus camera Suprime-Cam on the
Subaru 8.2m telescope during February-April of 2001 and 2002.
CDFSAGNCXO Catalog
This table contains the results of a detailed X-ray spectral analysis of the
sources in the 1 Ms catalog of the Chandra Deep Field South (CDFS, Giacconi
et al. 2002, CDS Cat. J/ApJS/139/369, available in Browse as the CHANDFS1MS
table), taking advantage of optical spectroscopy and photometric redshifts
for 321 extragalactic sources out of the total sample of 347 sources. As a
default spectral model, the authors adopt a power law with a slope Gamma with
an intrinsic redshifted absorption NH, a fixed Galactic absorption and an
unresolved Fe emission line. For 82 X-ray bright sources, they are able to
perform the X-ray spectral analysis leaving both Gamma and NH free. The
weighted mean value for the slope of the power law is 1.75 +/- 0.02, and the
distribution of best fit values shows an intrinsic dispersion of 0.30. The
authors do not find hints of a correlation between the spectral index Gamma
and the intrinsic absorption column density NH. They then investigate the
absorption distribution for the whole sample, deriving the NH values in
faint sources by fixing Gamma to be 1.8. The authors find that the fraction
of absorbed sources (with NH > 1022 cm-2) in the sample is constant (at
the level of about 75%) or moderately increasing with redshift. Finally, they
compare the optical classification to the X-ray spectral properties,
confirming that the correspondence of unabsorbed (absorbed) X-ray sources to
optical type I (type II) AGN is accurate for at least 80% of the sources with
spectral identification (1/3 of the total X-ray sample).
CENACXO Catalog
This table contains the results from two Chandra X-ray Observatory
observations of the X-ray point source population in the nearby radio galaxy
Centaurus A (NGC 5128). Using a wavelet decomposition detection algorithm,
246 individual point sources are detected above a limiting luminosity of
~ 2 * 10^36 ergs/s, 82 of which are detected in both data sets where the
fields of view overlap. Thirty-eight sources were detected in only one
observation but were within the field of view of both pointings, implying
considerable variability. Eight foreground stars were identified in these
observations, and nine of the sources were identified with known globular
clusters in Centaurus A. All previously observed ROSAT sources within our
field of view were detected. The faintest source in this table has
5 counts, which corresponds to a limiting luminosity of ~2.2 x 10^36
erg/s at the center of the field of view.
The two observations of Cen A were made with the ACIS-I array (observation
IDs were 00316 and 00962) on 1999 December 5 and 2000 May 17, with 35.9
36.5 ks exposures, respectively.
CEPBOB3CXO Catalog
This table contains the Cepheus B star formation region (the Cep B molecular
cloud and the Cep OB3b OB association) Chandra X-Ray point source catalog.
The Cepheus B (Cep B) molecular cloud and a portion of the nearby Cep OB3b OB
association, one of the most active regions of star formation within 1 kpc,
have been observed with the ACIS detector on board the Chandra X-Ray
Observatory. 431 X-ray sources have been detected, of which 89% are
confidently identified as clustered pre-main-sequence (PMS) stars. Two main
results are obtained. First, the best census to date for the stellar
population of the region has been made, with many members of two rich stellar
clusters, the lightly obscured Cep OB3b association and the deeply embedded
cluster in Cep B, whose existence was previously traced only by a handful of
radio sources and T Tauri stars, being identified. Second, a discrepancy
between the X-ray luminosity functions of the Cep OB3b and the Orion Nebula
cluster has been found. This may be due to the different initial mass
functions of the two regions (an excess of ~=0.3 M_solar stars) or different
age distributions. Several other results are obtained. A diffuse X-ray
component seen in the field is attributed to the integrated emission of
unresolved low-mass PMS stars. The X-ray emission from HD 217086 (O7n), the
principle ionizing source of the region, follows the standard model,
involving many small shocks in an unmagnetized radiatively accelerated wind.
X-ray source 294 joins a number of similar superflare PMS stars for which
long magnetic structures may connect the protoplanetary disk to the stellar
surface.
The Chandra observation of Cep B and Cep OB3b was obtained on 2003 March
11.51-11.88 with the ACIS camera. Only results from the imaging array
(ACIS-I) covering about 17' x 17' on the sky are considered here. The aim
point of the array was 22 56 49.4 +62 39 55.6 (J2000.0 RA and Dec), and the
satellite roll angle was 7.9 degrees. The total net exposure time was 30
ksec, with no background flaring or data losses.
CEPBOB3OID Catalog
The Cepheus B (Cep B) molecular cloud and a portion of the nearby Cep OB3b OB
association, one of the most active regions of star formation within 1 kpc,
have been observed with the Infrared Array Camera (IRAC) detector on board
the Spitzer Space Telescope. The goals were to study protoplanetary disk
evolution and processes of sequential triggered star formation in the region.
Out of ~400 pre-main-sequence (PMS) stars selected with an earlier Chandra
X-ray Observatory observation, ~95% are identified with mid-infrared sources
and most of these are classified as diskless or disk-bearing stars. The
discovery of the additional >200 IR-excess low-mass members gives a combined
Chandra+Spitzer PMS sample that is almost complete down to 0.5 * Msun
outside of the cloud, and somewhat above 1 * Msun in the cloud.
The X-ray observations of the Cep B/Cep OB3b region and their data analysis
are described in detail by Getman et al. (2006, CDS Cat. J/ApJS/163/306,
HEASARC CEPBOB3CXO table). The 30 ks exposure was obtained on 2003 March
11.51-11.88 with the Advanced CCD Imaging Spectrometer (ACIS) detector on
board the Chandra X-ray Observatory as part of the ACIS Instrument Team's
Guaranteed Time Observations (ObsId No. 3502, P.I.: G. Garmire). The mid-IR
observation of Cep B and Cep OB3b was obtained on 2007 February 18 with the
IRAC detector on the Spitzer Space Telescope in the 3.6, 4.5, 5.8, and 8.0
micron channels. This was a General Observer project (program identification
No. 30361; P.I.: J. Wang).
This table contains the optical and infrared counterpart information on the
431 X-ray sources detected by Chandra. It does not contain the 224 IR-excess
objects which were not detected as X-ray sources (listed in Table 3 of the
reference paper) that are thought to be additional low-mass members of this
complex.
CG12CXO Catalog
The mysterious high Galactic latitude cometary globule CG 12 has been
observed with the ACIS detector on board the Chandra X-Ray Observatory. 128
X-ray sources are detected, of which half are likely young stars formed
within the globule's head. This new population of >~ 50 T Tauri stars and
one new embedded protostar is far larger than the previously reported few
intermediate-mass and two protostellar members of the cloud. Most of the
newly discovered stars have masses of 0.2-0.7 Msolar, and 9% - 15% have
K-band excesses from inner protoplanetary disks. X-ray properties provide an
independent distance estimate consistent with the unusual location of CG 12
>~200 pc above the Galactic plane. The star formation efficiency in CG 12
appears to be 15% - 35%, far above that seen in other triggered molecular
globules. The median photometric age found for the T Tauri population,
assuming Siess et al. (2000, A&A, 358, 593) isochrones, is ~4 Myr with a
large spread of <1 - 20 Myr and ongoing star formation in the molecular
cores. The stellar age and spatial distributions are inconsistent with a
simple radiation-driven implosion (RDI) model and suggest either that CG
12 is an atypically large shocked globule or that it has been subject to
several distinct episodes of triggering and ablation. In their paper the
authors report a previously unnoticed group of B-type stars northwest of
CG 12 that may be the remnants of an OB association that produced multiple
supernova explosions that could have shocked and ablated the cloud over a
15 - 30 Myr period. HD 120958 (B3e), the most luminous member of the group,
may be currently driving an RDI shock into the CG 12 cloud.
The current project combines four X-ray observations of the globule:
Field ObsID Start Time Expo. R.A. Decl. Roll Angle
(UT) (ks) (J2000.0) (deg)
I.... 6423 2006 Apr 15 16:19:17 30.8 13 57 44.52 39 58 48.31 11.5
II... 6424 2006 Jun 02 07:25:09 3.1 13 57 42.87 39 43 01.76 285.0
III.. 6425 2006 Apr 13 08:44:08 3.1 13 56 19.40 39 42 47.94 14.7
IV... 6426 2006 Apr 15 12:54:20 3.1 13 56 19.40 39 58 48.09 11.1
where the units of right ascension are hours, minutes, and seconds, and the
units of declination are degrees, arcminutes, and arcseconds, ObsID values are
from the Chandra Observation Catalog, exposure times are the sum of Good Time
Intervals (GTIs) for the CCD at the telescope aim point (CCD3) minus 1.3% to
account for CCD readouts, and the aim points and roll angles are obtained from
the satellite aspect solution before astrometric correction was applied.
There is one primary field (I in Fig. 1 of the reference paper) with ~31 ks
exposure directed at the globule's core and three secondary fields (II, III,
and IV in Fig. 1) with ~3 ks exposures positioned contiguously to the north
and west of the core. The primary pointing is intended to detect the population
of pre-main sequence (PMS) stars forming in the molecular head of the globule.
The secondary pointings are designed to locate an older population of stars
expected if the present cloud is only the ablated remnant of a larger cloud
that experienced sequential star formation triggering events, similar to the
sequence of stars found in the authors' Chandra study of IC 1396N (Getman
et al. 2007, ApJ, 654, 316, available in Browse as the IC1396NCXO table).
Source searching was performed with data images and exposure maps constructed
at three spatial resolutions (0.5", 1.0", and 1.4" pixel-1) using the CIAO
wavdetect tool. The authors ran wavdetect with a low threshold P = 10-5,
which is highly sensitive but permits false detections at this point in the
analysis. This was followed by visual examination to locate other candidate
sources, mainly close doubles and candidate sources near the detection
threshold. Using ACIS Extract, photons were extracted within polygonal
contours of ~90% encircled energy using position-dependent models of the PSF.
The background was measured locally in source-free regions. Due to the very
low, spatially invariant ACIS-I background in the Chandra observations of
CG 12, there is a one-to-one correspondence between a source's significance
and net counts. Following the procedure of Getman et al. (2007, ApJ, 654,
316), the list of candidate sources ws trimmed to omit sources with fewer
than ~5 estimated source net counts, net full-band counts/PSF fraction <~ 4.5.
In the case of the CG 12 observations, the above criterion is equivalent to
accepting sources with a source significance of >~ 1.1. Thus, most of the
statistically insignificant source candidates found during the wavdetect step
were eliminated by the application of these source existence criteria.
For Chandra sources with > 20 net counts, the authors performed spectral
analysis with the XSPEC spectral fitting package version 12.2. The unbinned
source and background spectra were fitted with one-temperature APEC plasma
emission models using the maximum likelihood method. They assumed 0.3 times
solar elemental abundances previously suggested as typical for young stellar
objects (YSOs) in other star-forming regions. Solar abundances were taken from
Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197). X-ray absorption
was modeled using the atomic cross sections of Morrison & McCammon (1983,
ApJ, 270, 119). For absorbed thermal spectra characteristics of PMS stars,
the absorption NH can be estimated to roughly a factor of 2 precision
for 20 count sources.
CHAINTHCXO Catalog
This table contains the Chamaeleon (Cha) I North Cloud Chandra X-Ray point
source catalog. Sensitive X-ray imaging surveys provide a new and effective
tool to establish the census of pre-main-sequence (PMS) stars in nearby young
stellar clusters. A deep Chandra X-Ray Observatory (CXO) observation of PMS
stars in the Chamaeleon I North cloud achieved a limiting total-band X-ray
luminosity of log Lt ~ 1027 ergs/s (0.5 - 8 keV band) in a 0.8 x 0.8 pc2
region. Of the 107 X-ray sources, 37 are associated with Galactic stars, of
which 27 are previously recognized cloud members. These include 3 PMS brown
dwarfs: the protostellar brown dwarf ISO 192 has a particularly high level of
magnetic activity. Follow-up optical photometry and spectroscopy establish
that 9-10 of the Chandra sources are probably magnetically active background
stars. No new X-ray-discovered stars were confidently found despite the high
sensitivity of the Chandra observation. From these findings, the authors
argue that the sample of 27 PMS cloud members in the Chandra field is
uncontaminated and complete down to K = 12 or a stellar mass of about 0.1
solar masses.
A 16'x 16' region of the Cha I North cloud was observed with the imaging
array of the Advanced CCD Imaging Spectrometer (ACIS-I) detector on board the
Chandra X-Ray Observatory. The observation took place on 2001 July 2.25-3.04
UT with the detector aimpoint set at 11 10 00.0, -76 35 00 (J2000.0 RA and
Declination). The effective exposure was 66.3 ksec. The authors also obtained
VI-band CCD images of most of the ACIS field with the 1m telescope and CCD
detector at the South African Astronomical Observatory (SAAO) during 2002
February.
CHAMPHXAGN Catalog
This table contains the results from an X-ray and optical analysis
of 188 active galactic nuclei (AGN) identified from 497 hard X-ray
(observed flux in the (2.0 - 8.0 keV) band > 2.7 x 10-15 erg/cm2/s)
sources in 20 Chandra fields (1.5 square degrees) forming part of the
Chandra Multiwavelength Project (ChaMP). These medium-depth X-ray observations
enable the detection of a representative subset of those sources responsible
for the bulk of the 2 - 8 keV cosmic X-ray background. Brighter than the
survey's optical spectroscopic limit, the authors achieve a reasonable degree
of completeness (77% of X-ray sources with counterparts r' < 22.5 have been
classified): broad emission-line AGNs (62%), narrow emission-line galaxies
(24%), absorption-line galaxies (7%), stars (5%), or clusters (2%).
To construct a pure AGN sample, the authors required the rest-frame 2.0-8.0
keV luminosity (uncorrected for intrinsic absorption) to exceed 1042 erg
s-1, thereby excluding any sources that may contain a significant stellar
or hot ISM component. The most luminous known star-forming or elliptical
galaxies attain at most LX = 1042 erg s-1. Since many of the
traditional optical AGN signatures are not present in obscured sources, high
X-ray luminosity becomes the authors' single discriminant for supermassive
black hole accretion. They believe that almost all of the NELGs and ALGs
harbor accreting SMBHs based on their X-ray luminosity. They find that 90% of
the identified ChaMP sources have luminosities above this threshold. These
selection criteria yield a sample of 188 AGNs from 20 Chandra fields with
f(2-8 keV) > 2.7 x 10-15 erg cm-2 s-1, r' < 22.5, and LX > 1042 erg
s-1. The authors removed five objects identified as clusters based on their
extended X-ray emission.
CHAMPLANE Catalog
The authors have carried out optical and X-ray spectral analyses on a sample
of 136 candidate optical counterparts of X-ray sources found in five Galactic
bulge fields included in their Chandra Multiwavelength Plane (ChaMPlane)
Survey. They used a combination of optical spectral fitting and quantile
X-ray analysis to obtain the hydrogen column density toward each object, and
a three-dimensional dust model of the Galaxy to estimate the most probable
distance in each case. They present the discovery of a population of stellar
coronal emission sources, likely consisting of pre-main-sequence, young
main-sequence, and main-sequence stars, as well as a component of active
binaries of RS CVn or BY Dra type. They identify one candidate quiescent
low-mass X-ray binary with a sub-giant companion, but note that this object
may also be an RS CVn system. They report the discovery of 3 new
X-ray-detected cataclysmic variables (CVs) in the direction of the Galactic
center (at distances <~2 kpc). This number is in excess of predictions made
with a simple CV model based on a local CV space density of <~10-5 pc-3,
and a scale height of ~200 pc. They discuss several possible reasons for this
observed excess in their paper.
CHAMPLANEX Catalog
This table contains the Chandra Multiwavelength Plane (ChaMPlane) Survey
catalog of X-ray point sources in the window and four Galactic bulge fields,
specifically all source detections with net counts >= 1 in the 0.3-8 keV
broad band. In the reference paper, the authors present the log N-log S
and spatial distributions of X-ray point sources in seven Galactic bulge
(GB) fields within 4 degrees of the Galactic center (GC). They compare the
properties of 1159 X-ray point sources discovered in their deep (100 ks)
Chandra observations of three low extinction Window fields near the GC
with the X-ray sources in the other GB fields centered around Sgr B2, Sgr
C, the Arches Cluster, and Sgr A* using Chandra archival data. To reduce
the systematic errors induced by the uncertain X-ray spectra of the sources
coupled with field-and-distance-dependent extinction, they classify the X-ray
sources using quantile analysis and estimate their fluxes accordingly. The
result indicates that the GB X-ray population is highly concentrated at
the center, more heavily than the stellar distribution models. It extends
out to more than 1.4 degrees from the GC, and the projected density follows
an empirical radial relation inversely proportional to the offset from the
GC. They also compare the total X-ray and infrared surface brightness using
the Chandra and Spitzer observations of the regions. The radial distribution
of the total infrared surface brightness from the 3.6-micron band images
appears to resemble the radial distribution of the X-ray point sources
better than that predicted by the stellar distribution models. Assuming
a simple power-law model for the X-ray spectra, the closer to the GC, the
intrinsically harder the X-ray spectra appear, but adding an iron emission
line at 6.7 keV in the model allows the spectra of the GB X-ray sources
to be largely consistent across the region. This implies that the majority
of these GB X-ray sources can be of the same or similar type. Their X-ray
luminosity and spectral properties support the idea that the most likely
candidate is magnetic cataclysmic variables (CVs), primarily intermediate
polars (IPs). Their observed number density is also consistent with the
majority being IPs, provided the relative CV to star density in the GB is
not smaller than the value in the local solar neighborhood.
CHAMPPSC Catalog
This table represents the `Main Chandra Multiwavelength Project
(ChaMP) X-Ray Point Source Catalog' and contains the basic parameters,
photometry, and fluxes of 6512 ChaMP sources in 130 Chandra observations from
Chandra Cycles 1 and 2. This table lists fluxes for 2 assumed spectral energy
distributions with the photon indices of Gamma=1.4 and Gamma=1.7. This
catalog was distributed by the ChaMP team based on the "Chandra Multiwavelength
Project: X-ray Point Source Catalog (Kim et al., 2007, ApJS, 169, 401)", and
was downloaded from http://hea-www.harvard.edu/CHAMP/.
If you have any comments/questions on this catalog, please contact
mkim @ cfa.harvard.edu or dkim @ cfa.harvard.edu.
The full Chandra Multiwavelength Project (ChaMP) X-ray point source catalog
lists ~ 6800 X-ray sources detected in 149 Chandra observations covering ~ 10
square degrees. The full ChaMP catalog sample is 7 times larger than the
initial published ChaMP catalog (Kim et al. 2004, ApJS, 150, 19). The exposure
times of the fields in this sample range from 0.9 to 124 ks, corresponding to
a deepest X-ray flux limit in the 0.5 - 8.0 keV band of 9 x 10^-16 ergs cm^-2
s^-1. The ChaMP X-ray data were uniformly reduced and analyzed with
ChaMP-specific pipelines and then carefully validated by visual inspection.
The ChaMP catalog includes X-ray photometric data in eight different energy
bands as well as X-ray spectral hardness ratios and colors, source reliability,
detection probability, and positional uncertainties. The false source detection
rate is ~1% of all detected ChaMP sources, while the detection probability is
better than ~ 95% for sources with counts >~ 30 and off-axis angle <5'. The
typical positional offset between ChaMP X-ray source and their SDSS optical
counterparts is 0.7" +/- 0.4", derived from ~ 900 matched sources.
This HEASARC table contains the main ChaMP catalog of 6512 X-ray point sources
in 130 ChaMP fields observed once and in the overlapping fields which had
the longest exposures. It does not contain the supplementary ChaMP catalog
of 853 sources in 19 ChaMP overlapping fields with shorter exposure times.
CHAMPSDSSA Catalog
The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra
Multiwavelength Project (ChaMP; Green et al. 2004, ApJS, 150, 43) currently
offers the largest and most homogeneously selected sample of nearby galaxies
for investigating the relations between X-ray nuclear emission, nebular line
emission, black hole masses, and the properties of the associated stellar
populations. The authors provide X-ray spectral fits and valid uncertainties
for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19).
They present in their paper novel constraints that both X-ray luminosity LX
and X-ray spectral energy distribution bring to the galaxy evolutionary
sequence HII -> Seyfert/Transition Object -> LINER -> Passive suggested by
optical data. In particular, the authors show that both LX and Gamma, the
slope of the power law that best fits the 0.5 - 8 keV spectra, are consistent
with a clear decline in the accretion power along the sequence, corresponding
to a softening of their spectra. This implies that, at z ~ 0, or at
low-luminosity active galactic nucleus (AGN) levels, there is an
anticorrelation between Gamma and L/LEdd, opposite to the trend which is
exhibited by high-z AGN (quasars). The turning point in the Gamma - L/LEdd
LLAGN + quasars relation occurs near Gamma ~ 1.5 and L/LEdd ~ 0.01.
Interestingly, this is identical to what stellar mass X-ray binaries exhibit,
indicating that the authors have probably found the first empirical evidence
for an intrinsic switch in the accretion mode, from advection-dominated flows
to standard (disk/corona) accretion modes in supermassive black hole
accretors, similar to what has been seen and proposed to happen in stellar
mass black hole systems. The anticorrelation the authors find between Gamma
and L/LEdd may instead indicate that stronger accretion correlates with
greater absorption. Therefore, the trend for softer spectra toward more
luminous, high-redshift, and strongly accreting (L/LEdd >~ 0.01)
AGNs/quasars could simply be the result of strong selection biases reflected
in the dearth of type 2 quasar detections.
The cross-match of all ChaMP sky regions imaged by Chandra/ACIS with the SDSS
DR4 spectroscopic footprint results in a parent sample of 15,955 galaxies on
or near a chip and a subset of 199 sources that are X-ray detected. Among
those, only 107 sources have an off-axis angle (OAA) Theta <0.2 degrees and
avoid ccd=8 due to high serial readout noise; these 107 objects comprise the
main sample that the authors employ for this study and that are listed in
this table.
The authors performed direct spectral fits to the X-ray counts distribution
using the full instrument calibration, known redshift, and Galactic 21-cm
column nHGal. Source spectra were extracted from circular regions with
radii corresponding to energy encircled fractions of ~90%, while the
background region encompasses a 20 arcsec annulus, centered on the source,
with separation 4 arcsecs, from the source region. Any nearby sources were
excised, from both the source and the background regions. The spectral
fitting was done via yaxx ('Yet Another X-ray eXtractor': Aldcroft 2006,
BAAS, 38, 376), an automated script that employs the CIAO Sherpa tool. Each
spectrum was fitted in the range 0.5 - 8 keV by two different models: (1) a
single power law plus absorption fixed at the Galactic 21-cm value (model
'PL'), and (2) a fixed power law of photon index Gamma = 1.9 plus intrinsic
absorption of column nH (model 'PLfix'). For the nine objects with more than
200 counts, the authors employed a third model in which both the slope of the
power law and the intrinsic absorption were free to vary (model 'PL_abs').
CHANDFN1MS Catalog
This table is the Chandra Deep Field North 1-Megasecond Catalog.
It lists point sources detected in an extremely deep X-ray survey (1 Ms) of
the Hubble Deep Field North (HDF-N) and its environs (~450 square arcminutes)
which has been performed with the Advanced CCD Imaging Spectrometer on
board the Chandra X-Ray Observatory. This is one of the two deepest X-ray
surveys ever performed; for point sources near the aim point, it reaches
0.5 - 2.0 keV and 2 - 8 keV flux limits of ~3 x 10^-17 and ~2 x 10^-16 ergs
cm-2 s-1, respectively. 370 distinct point sources have been detected: 360 in
the full (0.5 - 8.0 keV) band, 325 in the soft (0.5 - 2.0 keV) band, 265 in
the hard (2 - 8 keV) band, and 145 in the ultrahard (4 - 8 keV) band. Source
positions are accurate to within 0.6 - 1.7 arcseconds (at ~90% confidence),
depending mainly on the off-axis angle. Source densities of 7100 (+1100, -940)
deg^-2 (at 4.2 x 10^-17 ergs cm^-2 s^-1) and 4200 (+670, -580) deg^-2 (at
3.8 x 10^-16 ergs cm^-2 s^-1) are observed in the soft and hard
bands, respectively.
CHANDFN2MS Catalog
The Chandra Deep Field North (CDFN) 2-Megasecond Catalog contains
the point sources found in the ~2 Megasecond (Ms) exposure of the Chandra
Deep Field North, currently the deepest X-ray observation of the
universe in the 0.5 -8.0 keV band. Five hundred and three (503) X-ray
sources were detected over an ~448 square arcminute area in up to seven X-ray
bands. Twenty (20) of these X-ray sources lie in the central ~5.3 square
arcminute Hubble Deep Field North (13600 (+3800,-3000) sources/deg^2).
The on-axis sensitivity limits are ~2.5x10^-17 ergs/cm^2/s (0.5 - 2.0 keV)
and 1.4x10^-16 ergs/cm^2/s (2 - 8 keV). Source positions are determined
using matched-filter and centroiding techniques; the median positional
uncertainty is ~0.3". The X-ray colors of the detected sources indicate a
broad variety of source types, although absorbed AGN (including a small
number of possible Compton-thick sources) are clearly the dominant type.
The average backgrounds in the 0.5 - 2.0 keV and 2 - 8 keV bands are
0.056 and 0.135 counts Ms^-1 pixel^-1, respectively. The background count
distributions are very similar to Poisson distributions. This 2 Ms exposure
is approximately photon limited in all seven X-ray bands for regions close
to the aim point. This observation does not suffer from source confusion
within ~6 arcminutes of the aim point.
CHANDFS1MS Catalog
The Chandra Deep Field South (CDFS) 1-Megasecond Catalog is
the source catalog obtained from a 942 kilosecond exposure, using the Advanced
CCD Imaging Spectrometer (ACIS-I) on the Chandra X-ray Observatory.
Eleven individual pointings made between 1999 October and 2000 December
were combined to generate the final image used for object detection.
Catalog generation proceeded simultaneously using two different methods:
a method of the authors' own design using a modified version
of the SExtractor algorithm, and a wavelet transform technique
developed specifically for Chandra observations. The detection
threshold was set in order to have less than 10 spurious sources,
as assessed by extensive simulations. The catalog as published was
subdivided into four sections: the primary list consisting of objects
common to the two detection methods, two secondary lists containing
sources which were detected by either the SExtractor algorithm alone or
by the wavelet technique alone, and the fourth list consisting of possible
diffuse or extended sources. The flux limits at the aimpoint for the soft
(0.5 - 2 keV) and hard (2 - 10 keV) bands are 5.5 x 10^-17 erg/s/cm^2
and 4.5 x 10^-16 erg/s/cm^2, respectively. The total number of sources
is 346; out of them, 307 were detected in the 0.5 - 2 keV band, and 251
in the 2 - 10 keV band.
Optical identifications are also presented for the catalogued sources.
The primary optical data are R band imaging from VLT/FORS1 to a depth
of R ~ 26.5 (Vega). In regions of the field not covered by the VLT/FORS1
deep imaging, the authors use R-band data obtained with the Wide Field
Imager (WFI) on the ESO-MPI 2.2 m telescope, as part of the ESO Imaging
Survey (EIS), which cover the entire X-ray survey. The FORS1/Chandra
offsets are small, ~1 arcsecond. Coordinate cross-correlation finds 85%
of the Chandra sources covered by FORS1 R to have counterparts within
the 3-sigma error box (>~1.5 arcseconds, depending on off-axis angle
and X-ray signal-to-noise). The unidentified fraction of sources,
approximately 10% - 15%, is close to the limit expected from the observed
X-ray flux to R-band ratio distribution for the identified sample.
CHANDFS2MS Catalog
This table contains point-source catalogs for the ~2 Ms exposure of the
Chandra Deep Field-South (CDF-S) this is one of the two most sensitive
X-ray surveys ever performed. The survey covers an area of ~436 arcmin2
and reaches on-axis sensitivity limits of ~1.9 x 10-17 and ~1.3 x 10-16
erg cm-2 s-1 for the 0.5-2.0 and 2-8 keV bands, respectively. Four hundred
and sixty-two X-ray point sources (source_sample = 'Main CDF-S' in this table)
are detected in at least one of three X-ray bands that were searched; 135 of
these sources are new compared to the previous ~1 Ms CDF-S detections. Source
positions are determined using centroid and matched-filter techniques; the
median positional uncertainty is ~0.36". The X-ray-to-optical flux ratios
of the newly detected sources indicate a variety of source types; ~55% of
them appear to be active galactic nuclei, while ~45% appear to be starburst
and normal galaxies. This table contains, in addition to the main Chandra
catalog, the supplementary catalog of 86 X-ray sources (source_sample =
'CDF-S + E-CDF-S' in this table) in the ~2 Ms CDF-S footprint that was
created by merging the ~250 ks Extended Chandra Deep Field-South with the
CDF-S; this approach provides additional sensitivity in the outer portions
of the CDF-S. This table also contains a second supplementary catalog
(source_sample = 'Optically Bright' in this table) of 30 X-ray sources
which was constructed by matching lower significance X-ray sources to bright
optical counterparts (R < 23.8); the majority of these sources appear to be
starburst and normal galaxies. The total number of sources in this table,
which contains the main and 2 supplementary catalogs, is thus 578. Optical
R-band counterparts and basic optical and infrared photometry are provided for
the X-ray sources in the main and supplementary catalogs. The authors also
include existing spectroscopic redshifts for 224 of the X-ray sources. The
average backgrounds in the 0.5-2.0 and 2-8 keV bands are 0.066 and 0.167
counts Ms-1 pixel-1, respectively, and the background counts follow
Poisson distributions. The effective exposure times and sensitivity limits of
the CDF-S are now comparable to those of the ~2 Ms Chandra Deep Field-North
(CDF-N). In their paper, the authors also present cumulative number counts
for the main catalog and compare the results to those for the CDF-N. The
soft-band number counts for these two fields agree well with each other at
fluxes higher than ~2 x 10-16 erg cm-2 s-1, while the CDF-S number
counts are up to ~25% smaller than those for the CDF-N at fluxes below ~2
x 10-16 erg cm-2 s-1 in the soft band and ~2 x 10-15 erg cm-2
s-1 in the hard band, suggesting small field-to-field variations.
CHANDFS4MS Catalog
This table contains the main Chandra source catalog for the 4
megasecond (Ms) Chandra Deep Field-South (CDF-S), which is the deepest Chandra
survey to date and covers an area of 464.5 arcmin2. It contains 740 X-ray
sources that are detected with wavdetect at a false-positive probability
threshold of 10-5 in at least one of three X-ray bands (0.5-8 keV, full band;
0.5-2 keV, soft band; and 2-8 keV, hard band) and also satisfy a
binomial-probability source-selection criterion of P < 0.004 (i.e., the
probability of sources not being real is less than 0.004); this approach is
designed to maximize the number of reliable sources detected. A total of 300
main-catalog sources are new compared to the previous 2 Ms CDF-S main-catalog
(the HEASARC CHANDFS2MS table) sources. The authors determined X-ray source
positions using centroid and matched-filter techniques and obtained a median
positional uncertainty of ~0.42 arcseconds. In their paper, they also provided
a supplementary catalog (not included in this HEASARC table), which consists
of 36 sources that are detected with wavdetect at a false-positive probability
threshold of 10-5, satisfy the condition of 0.004 < P < 0.1, and have an
optical counterpart with R < 24. Multiwavelength identifications, basic
optical/infrared/radio photometry, and spectroscopic/photometric redshifts
are provided for the X-ray sources in the main and supplementary catalogs.
Seven hundred sixteen (~97%) of the 740 main-catalog sources have
multiwavelength counterparts, with 673 (~94% of 716) having either
spectroscopic or photometric redshifts. The 740 main-catalog sources span
broad ranges of full-band flux and 0.5-8 keV luminosity; the 300 new
main-catalog sources span similar ranges although they tend to be
systematically lower.
Basic analyses of the X-ray and multiwavelength properties of the sources
indicate that >75% of the main-catalog sources are active galactic nuclei
(AGNs); of the 300 new main-catalog sources, about 35% are likely normal and
starburst galaxies, reflecting the rise of normal and starburst galaxies at
the very faint flux levels uniquely accessible to the 4 Ms CDF-S. Near the
center of the 4 Ms CDF-S (i.e., within an off-axis angle of 3'), the observed
AGN and galaxy source densities have reached 9800 (+1300,-1100) deg-2 and
6900 (+1100,-900) deg-2, respectively. Simulations show that the main catalog
is highly reliable and is reasonably complete. The mean backgrounds (corrected
for vignetting and exposure-time variations) are 0.063 and 0.178 counts Ms-1
pixel-1 (for a pixel size of 0.492 arcseconds) for the soft and hard bands,
respectively; the majority of the pixels have zero background counts. The 4 Ms
CDF-S reaches on-axis flux limits of ~3.2 x 10-17, 9.1 x 10-18, and 5.5 x
10-17 erg cm-2 s-1 for the full, soft, and hard bands, respectively. An
increase in the CDF-S exposure time by a factor of ~2-2.5 would provide
further significant gains and probe key unexplored discovery space.
This HEASARC table comprises Table 3 from the reference paper, the Main
Chandra Source Catalog of 740 X-ray sources. The 36 optically bright Chandra
sources that were listed in Table 6 of the reference paper are thus not
included herein.
CHANDFS7MS Catalog
This table contains the X-ray source catalogs for the ~7 Ms exposure of the
Chandra Deep Field-South (CDF-S), which covers a total area of 484.2 square
arcminutes. Utilizing WAVDETECT for initial source detection and ACIS Extract
for photometric extraction and significance assessment, the authors have
created a main source catalog (entries with source_sample = 'M' in this
HEASARC table) containing 1,008 sources that are detected in up to three
X-ray bands: 0.5-7.0 keV, 0.5-2.0 keV, and 2-7 keV. A supplementary source
catalog entries with source_sample = 'S' in this HEASARC table) is also
provided, including 47 lower-significance sources that have bright (Ks <~
23m) near-infrared (NIR) counterparts. The authors have identified
multiwavelength counterparts for 992 (98.4%) of the 1,008 main-catalog
sources, and they have collected redshifts for 986 of these sources,
including 653 spectroscopic redshifts and 333 photometric redshifts.
Based on the X-ray and multiwavelength properties, the authors have
identified 711 active galactic nuclei (AGNs) from the main-catalog sources.
Compared to the previous ~4 Ms CDF-S catalogs, 291 of the main-catalog
sources are new detections. The observations utilized in this survey have
achieved unprecedented X-ray sensitivity with average flux limits over the
central ~1 arcmin2 region of ~1.9 x 10-17, 6.4 x 10-18, and 2.7 x
10-17 erg cm-2 s-1 in the three X-ray bands, respectively. In the
reference paper, the authors provide cumulative number-count measurements
observing, for the first time, that normal galaxies start to dominate the
X-ray source population at the faintest 0.5-2.0 keV flux levels. The highest
X-ray source density reaches ~50,500 deg-2, and 47% +/- 4% of these sources
are AGNs (~23,900 deg-2).
The authors adopted a binomial no-source probability value, PB < 0.007 as
the criterion to prune their initial candidate source list and generate a
main source catalog, which includes 1,008 sources with a ~97%
multiwavelength-identification rate. This adopted PB threshold will have
inevitably rejected real X-ray sources. To recover some of these real
sources, the authors created a supplementary source catalog that contains
lower-significance X-ray sources that have bright optical/NIR counterparts;
the chance of a bright optical/NIR source being associated with a spurious
X-ray detection is quite small. A total of 47 candidate CDF-S sources having
0.007 <= PB < 0.1 are associated with bright, Ks <= 23m, TENIS sources,
where the false-match rate is only 1.7%, and these 47 sources constitute the
supplementary catalog.
A Galactic column density of NH,Gal = 8.8 * 1019 cm-2 along the line of
sight to the CDF-S is assumed in this study. All quoted magnitudes are in the
AB system. A cosmology with H0 = 67.8 km s-1 Mpc-1, OmegaM = 0.308,
and OmegaLambda = 0.692 (Planck Collaboration et al. 2016 values) is used
to calculate luminosities.
This HEASARC table contains the 1,008 sources from the main Chandra source
catalog (these entries are identified by the HEASARC-created source_sample
parameter being set to 'M' in this table) and the 47 lower-significance
sources from the supplementary NIR-bright Chandra source catalog (these
entries are identified by the HEASARC-created source_sample parameter being
set to 'S' in this table). This table thus has 1,055 entries.
CHANEXTDFS Catalog
This table contains the combined point-source catalogs for the
Extended Chandra Deep Field- South (E-CDF-S) survey. The E-CDF-S consists of
four contiguous 250 ks Chandra observations covering an approximately square
region of total solid angle ~0.3 square degrees, which flank the existing ~1
Ms Chandra Deep Field-South (CDF-S). The survey reaches sensitivity limits of
~1.1 x 10^-16 and ~6.7 x 10^-16 ergs cm^-2 s^-1 for the 0.5-2.0 and 2-8 keV
bands, respectively. 762 distinct X-ray point sources are detected within the
E-CDF-S exposure; 589 of these sources are new (i.e., not previously
detected in the ~1 Ms CDF-S). This brings the total number of X-ray
point sources detected in the E-CDF-S region to 915 (via the E-CDF-S and
~1 Ms CDF-S observations). Source positions are determined using
matched-filter and centroiding techniques; the median positional
uncertainty is ~0.35". The basic X-ray and optical properties of these
sources indicate a variety of source types, although absorbed active
galactic nuclei (AGNs) seem to dominate. In addition to the main Chandra
catalog, this table contains the supplementary source catalog with 33
lower-significance X-ray point sources that have bright optical
counterparts (R < 23 mag). These sources generally have X-ray-to-optical
flux ratios expected for normal and starburst galaxies, which lack a
strong AGN component. The basic number-count results for the main
Chandra catalog are in good agreement with the ~1 Ms CDF-S for sources
with 0.5-2.0 and 2-8 keV fluxes greater than 3 x 10^-16 and 1 x 10^-15 ergs
cm^-2 s^-1, respectively.
This HEASARC table contains 809 entries: 762 entries corresponding to the 762
sources listed in the main catalog (Table 2 of the published paper), 14
sources from the cross-field source list (Table 3) which give properties for
sources which were detected in more than one observational sources, e.g.
there are two entries for the source with source_number = 367, one
entry coming from the main catalog, the other entry from the cross-field
catalog, and 33 entries corresponding to the 33 sources in the supplementary,
optically bright source catalog (Table 6). The HEASARC has created a new
parameter called source_type to identify from which of these 3 original
tables any given entry comes from; it is set to 'main', 'crossfield' and
'supplement' for entries from Tables 2, 3, and 6, respectively.
CHANGALXRB Catalog
The authors of this catalog presented new Chandra constraints on the X-ray
luminosity functions (XLFs) of X-ray binary (XRB) populations, as well as
their scaling relations, for a sample of 38 nearby galaxies (D = 3.4-29 Mpc).
The galaxy sample is drawn primarily from the Spitzer Infrared Nearby
Galaxies Survey (SINGS) and contains a wealth of Chandra (5.8 Ms total) and
multiwavelength data, allowing for star formation rates (SFRs) and stellar
masses (M*) to be measured on subgalactic scales. The authors divided the
2478 X-ray-detected sources into 21 subsamples in bins of specific SFR
(sSFR=SFR/M*) and constructed XLFs. To model the XLF dependence on sSFR,
they fitted a global XLF model, containing contributions from high-mass XRBs
(HMXBs), low-mass XRBs (LMXBs), and background sources from the cosmic X-ray
background that respectively scale with SFR, M*, and sky area. They found an
HMXB XLF that is more complex in shape than previously reported and an LMXB
XLF that likely varies with sSFR, potentially due to an age dependence. When
applying the global model to XLF data for each individual galaxy, the authors
discovered a few galaxy XLFs that significantly deviated from their model
beyond statistical scatter. Most notably, relatively low-metallicity galaxies
have an excess of HMXBs above ~1038erg/s, and elliptical galaxies that have
relatively rich populations of globular clusters (GCs) show excesses of LMXBs
compared to the global model. Additional modeling of how the XRB XLF depends
on stellar age, metallicity, and GC specific frequency is required to
sufficiently characterize the XLFs of galaxies.
In this work, the authors utilized 5.8 Ms of Chandra ACIS data, combined with
UV-to-IR observations, for 38 nearby (D < ~30 Mpc) Spitzer Infrared Nearby
Galaxies Survey (SINGS; Kennicutt+
2003PASP..115..928K)
galaxies to revisit scaling relations of the HMXB and LMXB X-ray luminosity
functions (XLFs) with SFR and M*, respectively.
This table contains the X-ray properties for 4442 X-ray point sources,
including those with LX < 1035erg/s, which were excluded from the XLF
analysis.
CHANGBSCAT Catalog
This table contains the Chandra source list for the entire area of the
Galactic Bulge Survey (GBS) based on the lists provided in Jonker et al.
(2011, ApJ, 194, 18: Paper I) and Jonker et al. (2014, ApJS, 210, 18: Paper
II). The previous version of this table, based solely on the data presented
in Paper I, contained the Chandra source list based on the first
three-quarters of the GBS that had been observed as of the date of writing of
that paper.
Among the goals of the GBS are constraining the neutron star (NS) equation of
state and the black hole (BH) mass distribution via the identification of
eclipsing NS and BH low-mass X-ray binaries (LMXBs). The latter goal will, in
addition, be obtained by significantly enlarging the number of BH systems for
which a BH mass can be derived. Further goals include constraining X-ray
binary formation scenarios, in particular the common envelope phase and the
occurrence of kicks, via source-type number counts and an investigation of
the spatial distribution of X-ray binaries, respectively.
The GBS targets two strips of 6 degrees by 1 degrees (12 deg2 in total),
one above (1o < b < 2o) and the other below (-2o < b < -1o) the
Galactic plane in the direction of the Galactic center at X-ray, optical and
near-infrared wavelengths. By avoiding the Galactic plane (-1o < b < 1o)
the authors limit the influence of extinction on the X-ray and optical
emission but still sample relatively large number densities of sources. The
survey is designed such that a large fraction of the X-ray sources can be
identified from their optical spectra. The X-ray survey, by design, covers a
large area on the sky while the depth is shallow, using 2 ks per Chandra
pointing. In this way, the authors maximize the predicted number ratio of
(quiescent) LMXBs to cataclysmic variables. The survey is approximately
homogeneous in depth to a 0.5-10 keV flux of 7.7 x 10-14 erg cm-2 s-1.
As of Paper I, the authors had covered about three-fourths (8.3 deg2) of the
projected survey area with Chandra observations providing 1234 unique X-ray
sources. In Paper II, the authors find 424 additional X-ray sources in the 63
Chandra observations that they report on there. In the papers, the authors
discuss the characteristics and the X-ray variability of the brightest of the
sources as well as the radio properties from existing radio surveys. They
point out an interesting asymmetry in the number of X-ray sources as a
function of their Galactic l and b coordinates which is probably caused by
differences in average extinction towards the different parts of the GBS
survey area.
CHANMASTER Catalog
This database table contains all of the observations made by the Chandra
X-Ray Observatory (CXO, formerly known as the Advanced X-ray Astrophysics
Facility or AXAF) as part of the Performance Verification and Calibration
(PVC) phase and also contains all of the subsequent Cycles' Guaranteed Time
Observers (GTO) and General Observer (GO) targets, and any Director's
Discretionary Time (DDT) targets that have been observed. It also includes
scheduled and as-yet-not-scheduled targets.
The HEASARC updates this database table on a twice-weekly basis by querying
the database table at the Chandra X-Ray Center (CXC) website, as discussed in
the Provenance section. For observations whose status is 'archived', data
products can be retrieved from the HEASARC's mirror of the CXC's Chandra Data
Archive (CDA). The CXC should be acknowledged as the source of Chandra data.
The PVC phase was during the first few months of the CXO mission; some of the
calibration observations that are for monitoring purposes will be performed
in later mission cycles. All calibration data (entries with Type = CAL in
this database) are placed immediately into the CXO public data archive at the
Chandra X-Ray Observatory Center (CXC); please see the Web page at
http://asc.harvard.edu/ for more information on the CXC data archive). GTO
observations during Cycle 1 or any subsequent Cycle will probably occupy 100%
of months 3-4, 30% of months 5-22, and 15% of the available time for the
remainder of the mission. Guaranteed Time Observers will have the same
proprietary data rights as General Observers (i.e., their data will be placed
in the public CXC archive 12 months after they have received the data in
usable form).
For detailed information on the Chandra Observatory and datasets see:
http://cxc.harvard.edu/ for general Chandra information
http://cxc.harvard.edu/cda/ for the Chandra Data Archive
http://cxc.harvard.edu/cal/ for calibration information
http://cxc.harvard.edu/caldb/ for the calibration database
http://cxc.harvard.edu/ciao/ for data analysis
http://cxc.harvard.edu/ciao/download/ for analysis software
http://cxc.harvard.edu/ciao/threads/ for analysis threads
http://cda.harvard.edu/chaser/ for WebChaSeR
CHANNSGPSC Catalog
Emission from discrete point sources dominates the X-ray
luminosity in spiral galaxies. This table contains the results from a survey
of 11 nearby, nearly face-on spiral galaxies observed with the Chandra X-ray
Observatory in 22 observations for a total of 869 ks.
The galaxies in this sample are at high Galactic latitude to minimize the
absorbing column in the line of site, are nearby to minimize source confusion,
and span the Hubble sequence for spirals (types 0-7), allowing
insights into the X-ray source population of many diverse systems.
More than 820 unique point sources are detected in at least one observation
within the D25 ellipses of the galaxies. A minimum of 27% of the sources
exhibit detectable long- or short-term variability, indicating a source
population dominated by accreting XRBs. 17 ultraluminous X-ray
sources are detected, with typical rates per galaxy of 1 or 2.
In this table, source lists for the 11 galaxies are presented, along with
source counts, fluxes, luminosities, X-ray colors, and variability properties.
It should be noted that the X-ray source counts presented in this table
are raw, background-subtracted counts, so the count rates in sources from the
same galaxy that fall on different CCDs cannot be directly compared. The
colors presented have been corrected for the differences between
front-illuminated and back-illuminated CCDs.
CHANSEXAGN Catalog
The authors compare the relative merits of active galactic nuclei (AGN)
selection at X-ray and mid-infrared wavelengths using data from moderately
deep fields observed by both Chandra and Spitzer. The X-ray-selected AGN
sample and associated photometric and spectroscopic optical follow-up are
drawn from a subset of fields studied as part of the Serendipitous
Extragalactic X-ray Source Identification (SEXSI) program. Mid-infrared data
in these fields are derived from targeted and archival Spitzer imaging, and
mid-infrared AGN selection is accomplished primarily through application of
the Infrared Array Camera (IRAC) color-color AGN "wedge" selection technique.
Nearly all X-ray sources in these fields which exhibit clear spectroscopic
signatures of AGN activity have mid-infrared colors consistent with IRAC AGN
selection. These are predominantly the most luminous X-ray sources. X-ray
sources that lack high-ionization and/or broad lines in their optical spectra
are far less likely to be selected as AGNs by mid-infrared color selection
techniques. The fraction of X-ray sources identified as AGN in the
mid-infrared increases monotonically as the X-ray luminosity increases.
Conversely, only 22% of mid-infrared-selected AGN are detected at X-ray
energies in the moderately deep (t_exp_n~ 100 ks) SEXSI Chandra data.
The authors have expanded the multi-wavelength data available for six SEXSI
fields by obtaining Spitzer imaging observations. All six fields have deep
Chandra X-ray images, optical imaging, and extensive, deep optical
spectroscopy -- all of which has been published in Harrison et al. (2003,
ApJ, 596, 944), Eckart et al. (2005, ApJS, 156, 35), and Eckart et al. (2006,
ApJS, 165, 19). The authors obtained mid-infrared imaging through both
archival and targeted Spitzer programs which include imaging at 3.6, 4.5,
5.8, and 8 micron (um) from IRAC (PID 00017, 00064, 20694 and 20808), and
imaging at 24 um from MIPS (PID 20808 and 00083). This table contains mid-IR
photometric data for 290 hard X-ray-selected SEXSI sources. Each of the four
IRAC catalogs as well as the MIPS catalog was individually matched to the
SEXSI X-ray source positions using a 2.5 arcseconds search radius. To
calculate a false match rate, the authors shifted the X-ray source catalog by
1' and matched to the IRAC and MIPS catalogs; this entire procedure was
repeated 6 times using different 1' shifts. The resulting false match rates
were 10.1% (3.6 um), 7.2% (4.5 um), 3.7% (5.8 um), 2.6% (8.0 um), 1% (24 um),
and <1% for four-band-detected IRAC sources.
CHANSEXOID Catalog
The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program
is designed to expand significantly the sample of identified extragalactic
hard X-ray sources at intermediate fluxes, 10-15 ergs/cm2/s < 2-10 keV
Flux <~ 10-13 ergs/cm2/s. SEXSI, which includes sources derived from more
than 2 square degrees of Chandra images, provides the largest hard
X-ray-selected sample yet studied, offering an essential complement to the
Chandra Deep Fields (total area of 0.2 square degrees). In Eckart et al.
(2005, Paper II) R-band optical imaging of the SEXSI fields from the Palomar
P60 and P200, the MDM 2.4m and 1.3m, and the Keck I telescopes is described.
The authors have identified counterparts or derived flux limits for nearly
1000 hard X-ray sources. Using the optical images, they have derived accurate
source positions. They have investigated correlations between optical and
X-ray flux, and optical flux and X-ray hardness ratio. They have also studied
the density of optical sources surrounding X-ray counterparts, as well as the
properties of optically faint, hard X-ray sources. In Eckart et al. (2006,
Paper III) optical spectra of 477 counterparts are presented. These spectra
reach to R-band magnitudes of <~24 and have produced identifications and
redshifts for 438 hard X-ray sources. Typical completeness levels in the 27
Chandra fields studied are 40-70%. The vast majority of the 2-10 keV selected
sample are AGNs with redshifts between 0.1 and 3; the highest redshift source
lies at z = 4.33.
This table which combines data presented in Eckart et al. (2005, 2006) has
links to the list of SEXSI X-ray sources (the HEASARC Browse table CHANSEXSI:
see Paper I = Harrison et al. 2003, ApJ, 596, 944).
CHANSEXSI Catalog
The Serendipitous Extragalactic X-Ray Source Identification (SEXSI) program
is designed to extend greatly the sample of identified extragalactic hard
X-ray (2 - 10 keV) sources at intermediate fluxes (~10-13 to 10-15
erg/cm2/s). SEXSI, which studies sources selected from more than 2 deg2,
provides an essential complement to the Chandra Deep Fields, which reach
depths of 5 x 10-16 erg/cm2/s (2 - 10 keV) but over a total area of less
than 0.2 deg2. In their published paper, the authors describe the
characteristics of the survey and their X-ray data analysis methodology. They
present the cumulative flux distribution for the X-ray sample of 1034 hard
sources and discuss the distribution of spectral hardness ratios. Their log N
-log S in this intermediate flux range connects to those found in the Deep
Fields, and by combining the data sets, they constrain the hard X-ray
population over the flux range in which the differential number counts change
slope and from which the bulk of the 2 - 10 keV X-ray background arises. They
further investigate the log N - log S distribution separately for soft and
hard sources in the sample, finding that while a clear change in slope is
seen for the softer sample, the hardest sources are well described by a
single power law down to the faintest fluxes, consistent with the notion that
they lie at lower average redshift.
In the SEXSI program, fields were selected with high Galactic latitude
(|b| > 20 degrees) and with declinations accessible to the optical facilities
available to the authors (declination > -20 degrees). They used observations
taken with Chandra's Advanced Camera for Imaging Spectroscopy (ACIS I- and
S-modes; Bautz et al., 1998, Proc. SPIE, 3444, 210) only (for sensitivity in
the hard band). All the fields presented in this paper have data that are
available in the Chandra public archive.
CHANSNGCAT Catalog
The authors searched the public archive of the Chandra X-ray Observatory as
of 2016 March and assembled a sample of 719 galaxies within 50 Mpc with
available Advanced CCD Imaging Spectrometer observations. By
cross-correlation with the optical or near-infrared nuclei of these galaxies,
314 of them are identified to have an X-ray active galactic nucleus (AGN).
The majority of them are low-luminosity AGNs and are unlikely X-ray binaries
based upon their spatial distribution and luminosity functions. The AGN
fraction is around 60% for elliptical galaxies and early-type spirals, but
drops to roughly 20% for Sc and later types, consistent with previous
findings in the optical. However, the X-ray survey is more powerful in
finding weak AGNs, especially from regions with active star formation that
may mask the optical AGN signature. For example, 31% of the H II nuclei are
found to harbor an X-ray AGN. For most objects, a single power-law model
subject to interstellar absorption is adequate to fit the spectrum, and the
typical photon index is found to be around 1.8. For galaxies with a
non-detection, their stacked Chandra image shows an X-ray excess with a
luminosity of a few times 1037 erg/s on average around the nuclear region,
possibly composed of faint X-ray binaries. This paper reports on the
technique and results of the survey; in-depth analysis and discussion of the
results were to be reported in forthcoming papers, e.g., She et al. (2017,
ApJ, 842, 131).
The sample was assembled based on Chandra/ACIS observations that were
publicly available as of 2016 March. The authors first generated a full list
of ACIS observations, and then searched in the NASA/IPAC Extragalactic
Database (NED) for galaxies within 50 Mpc whose nuclear positions were less
than 8 arcminutes from the aim point of any Chandra observation. The adopted
distances were taken from NED, in the following order of priority: surface
brightness fluctuations, Cepheid variables, tip of the red giant branch, Type
Ia supernovae, the fundamental plane, Faber-Jackson relation, Tully-Fisher
relation. If more than one reference is available for the distance by the
same means, the latest one is selected, unless otherwise specified. Whenever
possible, the authors obtain positions of the galaxy nuclei based on
measurements from near-infrared images, which suffer from less obscuration by
dust or confusion from young star-forming regions. Most of the data come from
the Two-Micron All Sky Survey (2MASS) extended source catalog (Skrutskie et
al. 2006, AJ, 131, 1163), or NED otherwise. In a few cases, the NED positions
come from radio observations. The authors discarded galaxies whose nuclear
positions in NED were obtained from X-ray observations.
CHANTYPGPR Catalog
Using the Chandra Advanced CCD Imaging Spectrometer Imaging array (ACIS-I),
the authors carried out a deep hard X-ray observation of the Galactic plane
region at a location (l, b) ~ (28.5 degrees, 0.0 degrees), where no discrete
X-ray source had been reported previously. They detected 274 new point X-ray
sources (4-sigma or greater confidence in any of the 3 energy bands 0.5 - 3.0
keV, 3.0 - 8.0 keV or 0.5 - 8.0 keV), as well as strong Galactic diffuse
emission within two partially overlapping ACIS-I fields (~ 250 square
arcminutes in total). The point-source sensitivity was ~ 3 x 10-15
ergs/s/cm2 in the 2 - 10 keV band and ~ 2 x 10-16 erg/s/cm2 in the 0.5 -
2 keV band The sum of all the detected point-source fluxes accounts for only
~ 10% of the total X-ray flux in the field of view. Only 26 point sources
were detected in both the soft and hard bands, indicating that there are two
distinct classes of X-ray source distinguished by their spectral hardness
ratios. The surface number density of the hard sources is only slightly
higher than that measured in high Galactic latitude regions, indicating that
the majority of the hard sources are background AGNs.
Following up the Chandra observation, the authors performed a near-infrared
(NIR) survey with SofI at ESO/NTT. Almost all the soft X-ray sources have
been identified in the NIR, and their spectral types are consistent with
main-sequence stars, suggesting that most of them are nearby X-ray-active
stars. On the other hand, only 22% of the hard sources had near-IR
counterparts, which are presumably Galactic. From X-ray and near-IR spectral
study, they are most likely to be quiescent cataclysmic variables.
CHANULXCAT Catalog
One hundred fifty-five (the abstract in the paper erroneously states the
number to be 154) discrete, non-nuclear, ultraluminous X-ray (ULX) sources,
with spectroscopically determined intrinsic X-ray luminosities greater than
1039 erg/s, have been identified in 82 galaxies that were observed with
Chandra's Advanced CCD Imaging Spectrometer (ACIS). Positions, X-ray
luminosities, and spectral and timing characteristics of these ULXs are
contained in this table. Eighty-three percent of ULX candidates have spectra
that can be described as absorbed power laws with mean index Gamma = 1.74 and
column density NH = 2.24 x 1021 atoms cm-2, or ~5 times the average
Galactic column. About 20% of the ULXs have much steeper indices indicative
of a soft, and likely thermal, spectrum. The locations of ULXs in their host
galaxies are strongly peaked toward their galaxy centers. The deprojected
radial distribution of the ULX candidates is somewhat steeper than an
exponential disk, indistinguishable from that of the weaker sources. About
5%-15% of ULX candidates are variable during the Chandra observations (which
average 39.5 ks). Comparison of the cumulative X-ray luminosity functions of
the ULXs to Chandra Deep Field results suggests ~25% of the sources may be
background objects, including 14% of the ULX candidates in the sample of
spiral galaxies and 44% of those in elliptical galaxies, implying the
elliptical galaxy ULX population is severely compromised by background active
galactic nuclei. Correlations with host galaxy properties confirm the number
and total X-ray luminosity of the ULXs are associated with recent star
formation and with galaxy merging and interactions. The preponderance of ULXs
in star-forming galaxies as well as their similarities to less-luminous
sources suggest they originate in a young but short-lived population such as
the high-mass X-ray binaries, with a smaller contribution (based on spectral
slope) from recent supernovae. The number of ULXs in elliptical galaxies
scales with host galaxy mass and can be explained most simply as the
high-luminosity end of the low-mass X-ray binary population.
CHANVGUIDE Catalog
Variable stars have been identified among the optical-wavelength
light curves of guide stars used for pointing control of the Chandra X-ray
Observatory. The authors present a catalog of these variable stars along with
their light curves and ancillary data. Variability was detected to a lower
limit of 0.02 mag amplitude in the 4000-10000 Angstroms range using the
photometrically stable Aspect Camera on board the Chandra spacecraft. The
Chandra Variable Guide Star Catalog (VGUIDE) contains 827 stars, of which 586
are classified as definitely variable and 241 are identified as possibly
variable. Of the 586 definite variable stars, the authors believe 319 are new
variable star identifications. Types of variables in the catalog include
eclipsing binaries, pulsating stars, and rotating stars. The variability was
detected during the course of normal verification of each Chandra pointing and
results from analysis of over 75,000 guide star light curves from the Chandra
mission. The VGUIDE catalog represents data from only about 9 years
of the Chandra mission. Future releases of VGUIDE will include newly identified
variable guide stars as the mission proceeds. An important advantage of the
use of space data to identify and analyze variable stars is the relatively
long observations that are available. The Chandra orbit allows for
observations up to 2 days in length. Also, guide stars were often used
multiple times for Chandra observations, so many of the stars in the VGUIDE
catalog have multiple light curves available from various times in the
mission. The catalog is presented as both online data associated with this
paper (from which this HEASARC representation was created) and as a public Web
interface at http://cxc.harvard.edu/vguide/. Light curves with data at the
instrumental time resolution of about 2 s, overplotted with the data binned at
1 ks, can be viewed on the above-mentioned public Web interface and downloaded
for further analysis. (This HEASARC Browse table also contains links to these
light curves). VGUIDE is a unique project using data collected during the
mission that would otherwise be ignored. The stars available for use as
Chandra guide stars are generally 6-11 magnitudes and are commonly spectral
types A and later. Due to the selection of guide stars entirely for positional
convenience, this catalog avoids the possible bias of searching for
variability in objects where it is to be expected. Statistics of variability
compared to spectral type indicate the expected dominance of A-F stars as
pulsators. Eclipsing binaries are consistently 20%-30% of the detected var
iables across all spectral types.
CHESSCAT Catalog
The ChaMP Extended Stellar Survey (ChESS) X-ray catalog contains 348
X-ray-emitting stars identified from correlating the Extended Chandra
Multiwavelength Project (ChaMP), a wide-area serendipitous survey based on
archival X-ray images, with the Sloan Digital Sky Survey (SDSS). The authors
used morphological star/galaxy separation, matching to an SDSS quasar
catalog, an optical color-magnitude cut, and X-ray data-quality tests to
create this catalog, from a sample of 2121 matched ChaMP/SDSS sources. Their
cuts retain 92% of the spectroscopically confirmed stars in the original
sample while excluding 99.6% of the 684 spectroscopically confirmed
extragalactic sources. Fewer than 3% of the sources in their final catalog
are previously identified stellar X-ray emitters. For 42 catalog members,
spectroscopic classifications are available in the literature. New spectral
classifications and H-alpha measurements are presented for an additional 79
stars. The catalog is dominated by main-sequence stars; the authors estimate
the fraction of giants in ChESS to be ~10%. They identify seven giant stars
(including a possible Cepheid and an RR Lyrae star) as ChaMP sources, as well
as three cataclysmic variables. They derive distances from ~10 to 2000 pc for
the stars in the catalog using photometric parallax relations appropriate for
dwarfs on the main sequence and calculate their X-ray and bolometric
luminosities. These stars lie in a unique space in the LX-distance plane,
filling the gap between the nearby stars identified as counterparts to
sources in the ROSAT All Sky Survey and the more distant stars detected in
deep Chandra and XMM-Newton surveys. For 36 newly identified X-ray-emitting M
stars, the authors calculated LH-alpha/Lbol. The quantities
LH-alpha/Lbol and LX/Lbol are linearly related below LX/Lbol ~ 3
x 10-4, while LH-alpha/Lbol appears to turn over at larger LX/Lbol
values. Stars with reliable SDSS photometry have an ~0.1 mag blue excess in
u-g, likely due to increased chromospheric continuum emission. Photometric
metallicity estimates suggest that the sample is evenly split between the
young and old disk populations of the Galaxy; the lowest activity sources
belong to the old disk population, a clear signature of the decay of magnetic
activity with age.
CHICAGOCXO Catalog
This table contains results from the 'Chasing the Identification of ASCA
Galactic Objects' (ChIcAGO) survey, which is designed to identify the unknown
X-ray sources discovered during the ASCA Galactic Plane Survey (AGPS). Little
is known about most of the AGPS sources, especially those that emit primarily
in hard X-rays (2-10 keV) within the X-ray flux range from ~ 10-13 to
10-11 erg cm-2 s-1. In ChIcAGO, the sub-arcsecond localization
capabilities of Chandra have been combined with a detailed multi-wavelength
follow-up program, with the ultimate goal of classifying the > 100
unidentified sources in the AGPS. Overall to date, 93 unidentified AGPS
sources have been observed with Chandra as part of the ChIcAGO survey. A
total of 253 X-ray point sources have been detected in these Chandra
observations within 3 arcminutes of the original ASCA positions. The authors
have identified infrared and optical counterparts to the majority of these
sources, using both new observations and catalogs from existing Galactic
plane surveys. X-ray and infrared population statistics for the X-ray point
sources detected in the Chandra observations reveal that the primary
populations of Galactic plane X-ray sources that emit in the X-ray flux range
from ~ 10-13 to 10-11 erg cm-2 s-1 are active stellar coronae,
massive stars with strong stellar winds that are possibly in colliding wind
binaries, X-ray binaries, and magnetars. There is also another primary
population that is still unidentified but, on the basis of its X-ray and
infrared properties, likely comprises partly Galactic sources and partly
active galactic nuclei.
A total of 93 AGPS sources have been observed with Chandra as part of the
ChIcAGO survey, of which 84 were imaged with ACIS-S and 9 were imaged with
HRC-I. The ChIcAGO Chandra observations took place over a 3.5 yr period, from
2007 January to 2010 July. The Chandra exposure times ranged from ~ 1 to 10
ks. All the details of these Chandra observations are listed in Table 1 of
the reference paper. The initial automated analysis of these Chandra
observations was conducted using the ChIcAGO Multi-wavelength Analysis
Pipeline (MAP), described in Section 2.2 of the reference paper. ChIcAGO MAP
takes the ACIS-S or HRC-I Chandra observation of an AGPS source field and
detects and analyzes all point sources within 3 arcminutes, equivalent to the
largest likely position error, for the original AGPS source positions
supplied by Sugizaki et al. (2001, ApJS, 134, 77). The authors then performed
a more detailed X-ray analysis and counterpart study for those 74 sources
with > 20 X-ray counts, as such sources are approximately within the original
AGPS sources X-ray flux range (see Sections 3.2 and 3.3 of the reference
paper).
Infrared and optical follow-up were primarily performed on those ChIcAGO
sources having > 20 X-ray counts. In order to determine which optical and
infrared sources are counterparts to ChIcAGO sources, the authors used a
technique similar to that described by Zhao et al. (2005, ApJS, 161, 429),
using their Equation (11). If the separation between a ChIcAGO source's
wavdetect position and its possible counterpart is less than the quadratic
sum of their 3-sigma positional errors and the 3-sigma Chandra pointing
error, then the X-ray and optical (or infrared) sources are likely to be
associated. The 1-sigma positional errors for all sources in the 2MASS PSC
and GLIMPSE catalogs are 0.1 arcseconds and 0.3 arcseconds, respectively.
USNO B has an astrometric accuracy of < 0.25 arcseconds. The authors have
assumed that the error distributions of the Chandra observations, Chandra
pointing, and USNO B Catalog are all Gaussian for the purposes of identifying
possible counterparts to the ChIcAGO sources.
CHNGPSCLIU Catalog
The Chandra data archive is a treasure trove for various studies,
and in this study the author exploits this valuable resource to study the X-ray
point source populations in nearby galaxies. By 2007 December 14, 383 galaxies
within 40 Mpc with isophotal major axes above 1 arcminute had been observed by
626 public ACIS observations, most of which were for the first time analyzed
by this survey to study the X-ray point sources. Uniform data analysis
procedures were applied to the 626 ACIS observations and led to the detection
of 28,099 point sources, which belong to 17,559 independent sources. These
include 8700 sources observed twice or more and 1000 sources observed 10 times
or more, providing a wealth of data to study the long-term variability of these
X-ray sources. Cross-correlation of these sources with galaxy isophotes led to
8,519 sources within the D25 isophotes of 351 galaxies, 3,305 sources between
the D25 and 2 * D25 isophotes of 309 galaxies, and an additional 5,735
sources outside the 2 * D25 isophotes of galaxies.
This survey has produced a uniform catalog, by far the largest, of 11,824
X-ray point sources within 2 * D25 isophotes of 380 galaxies. Contamination
analysis using the log N-log S relation shows that 74% of the sources within
the 2 * D25 isophotes above 1039 erg s-1, 71% of the sources above
1038 erg s-1, 63% of the sources above 1037 erg s-1, and 56% of all
sources are truly associated with the galaxies. Meticulous efforts have
identified 234 X-ray sources with galactic nuclei of nearby galaxies. This
archival survey leads to 300 ultraluminous X-ray sources (ULXs) with LX in
the 0.3-8 keV band >= 2 x 1039 erg s-1 within the D25 isophotes, 179
ULXs between the D25 and the 2 * D25 isophotes, and a total of 479 ULXs
within 188 host galaxies, with about 324 ULXs truly associated with the host
galaxies based on the contamination analysis. About 4% of the sources exhibited
at least one supersoft phase, and 70 sources are classified as ultraluminous
supersoft sources with LX (0.3-8 keV) >= 2 x 1038 erg s-1. With a uniform
data set and good statistics, this survey enables future works on various
topics, such as X-ray luminosity functions for the ordinary X-ray binary
populations in different types of galaxies, and X-ray properties of galactic
nuclei.
This table contains the list of 17,559 'independent' X-ray point sources that
was contained in table 4 of the reference paper. As the author notes in Section
5 of this paper, there are 341 sources projected within 2 galaxies with
overlapping domains which are listed for both galaxies. The 5,735 sources
lieing outside the 2* D25 isophotes of the galaxies are also included in
this table. For these sources, the X-ray luminosities are computed as if they
were in a galaxy of that group, which may or may not be the case; thus, they
may not be their 'true' luminosities, but are listed for the purposes of
comparison.
CHPNGPTSRC Catalog
The authors have analyzed Chandra ACIS observations of 32 nearby spiral and
elliptical galaxies. The properties (e.g., counts in 3 energy bands, hardness
ratios and inferred X-ray luminosities) of the 1441 X-ray point sources that
were detected in these galaxies are listed in this table. The total
point-source X-ray (0.3 - 8.0 keV) luminosity LXP is found to be well
correlated with the B-band, K-band, and FIR+UV luminosities of spiral host
galaxies, and is well correlated with the B-band and K-band luminosities of
elliptical galaxies. This suggests an intimate connection between LXP and
both the old and the young stellar populations, for which K and FIR+UV
luminosities are reasonable proxies for the galaxy mass and the star
formation rate (SFR).
CLANS Catalog
This table contains the catalogs for the X-ray sources detected in the
Chandra Lockman Area North Survey (CLANS). (The information on the optical
and infrared counterparts to these sources is contained in the CLANSOID
table.) The nine ACIS-I fields which constitute the CLANS cover a solid angle
of ~0.6 deg2 and reach fluxes of 7 x 10-16 ergs cm-2 s-1 (0.5-2 keV)
and 3.5 x 10-15 ergs cm-2 s-1 (2-8 keV). The authors find a total of
761 X-ray point sources. The CLANS and CLASXS surveys bridge the gap between
the ultra-deep pencil-beam surveys, such as the CDFs, and the shallower, very
large-area surveys. As a result, they probe the X-ray sources that contribute
the bulk of the 2-8 keV X-ray background and cover the flux range of the
observed break in the log N-log S distribution.
CLANS consists of nine separate 70 ks Chandra ACIS-I exposures centered at
J2000.0 RA and Dec of (10 46,+59 01) (see Table 2 of the reference paper for
the full observational details) which were combined to create an 0.6 deg2
image containing 761 sources. The CLANS observations consist of a raster with
an ~2 arcminute overlap between contiguous pointings. Following the
prescription in Yang et al. (2004, AJ, 128, 1501) for the CLASXS field, the
authors merged the nine individual pointing catalogs to create the final
CLANS X-ray catalog. For sources with more than one detection in the nine
fields, they used the detection from the observation in which the effective
area of the source was the largest.
CLANSOID Catalog
This table contains the redshift catalog for the X-ray sources detected in
the Chandra Lockman Area North Survey (CLANS). The redshifts for the CLANS
field are all new. For fluxes above 10-14 ergs cm-2 s-1 (2-8 keV)
the authors have redshifts for 76% of the sources in the CLANS, CLASXS,
and CDF-N surveys. They extend the redshift information for the full sample
using photometric redshifts. The goal of the OPTX Project is to use these
three surveys, which are among the most spectroscopically complete surveys
to date, to analyze the effect of spectral type on the shape and evolution
of the X-ray luminosity functions and to compare the optical spectral types
with the X-ray spectral properties.
The optical and infrared photometric catalog for the CLANS X-ray sources is
presented here (see the CLANS Browse table for the X-ray information). The
CLANS and CLASXS surveys bridge the gap between the ultra-deep pencil-beam
surveys, such as the CDFs, and the shallower, very large-area surveys. As
a result, they probe the X-ray sources that contribute the bulk of the 2-8
keV X-ray background and cover the flux range of the observed break in the
log N - log S distribution.
CLASXS Catalog
This table contains the X-ray catalog and basic results from the wide-area,
moderately deep Chandra Large Area Synoptic X-ray Survey (CLASXS) of the
Lockman Hole-Northwest (LHNW) field (Yang et al. 2004), as well as the
results from optical and near-infrared photometric and spectroscopic
observations of these X-ray sources (Steffen et al. 2004).
The nine ACIS-I fields cover a contiguous solid angle of 0.4 square degrees
and reach fluxes of 5 x 10-16 ergs/cm2/s (0.4 - 2 keV) and 3 x 10-15
ergs/cm2/s (2 - 8 keV). (Note that fields LHNW 1-3 were observed during 2001
April 30-May 17, and that the rest of the fields were observed during 2002
April 29-May 4). This survey bridges the gap between ultra-deep pencil-beam
surveys, such as the Chandra Deep Fields (CDFs), and shallower, large-area
surveys, allowing a better probe of the X-ray sources that contribute most of
the 2 - 10 keV cosmic X-ray background (CXB). A total of 525 X-ray point
sources and four extended sources were found.
There are B, V, R, I, and z' photometry for 521 (99%) of the 525 sources in
the X-ray catalog and spectroscopic redshifts for 271 (52%), including
20 stars. The authors did not find evidence for redshift groupings of the
X-ray sources, like those found in the Chandra Deep Field surveys, because
of the larger solid angle covered by this survey. They separated the
X-ray sources by optical spectral type and examined the colors, apparent
and absolute magnitudes, and redshift distributions for the broad-line and
non-broad-line active galactic nuclei. Combining their wide-area survey with
other Chandra and XMM-Newton hard X-ray surveys, they find a definite lack of
luminous, high accretion rate sources at z < 1, consistent with previous
observations that showed that super-massive black hole growth is dominated at
low redshifts by sources with low accretion rates.
CLASXSOID Catalog
This table contains the redshift catalog for the X-ray sources detected in
the Chandra Large Area Synoptic X-ray Survey (CLASXS). The catalog for the
CLASXS field includes redshifts from previous work. The authors have extended
the redshift information for the full sample using photometric redshifts. The
goal of the OPTX Project is to use this survey, together with the Chandra
Deep Field-North (CDF-N) and the Chandra Lockman Area North Survey (CLANS),
which are among the most spectroscopically complete surveys to date, to
analyze the effect of spectral type on the shape and evolution of the X-ray
luminosity functions and to compare the optical spectral types with the X-ray
spectral properties. The CLANS and CLASXS surveys bridge the gap between the
ultra-deep pencil-beam surveys, such as the Chandra Deep Fields, and the
shallower, very large-area surveys. As a result, they probe the X-ray sources
that contribute the bulk of the 2-8 keV X-ray background and cover the flux
range of the observed break in the log N - log S distribution.
This table also contains updated optical and infrared photometric catalogs
for the X-ray sources in the CLASXS field. Note that for any source with both
CFHT and Subaru data in the R and z' bands, the authors used the CFHT
magnitude. Typical photometric uncertainties are given in Section 3.6 of the
reference paper (Trouille et al. 2008).
The X-ray information for the CLASXS catalog which was published in Yang et
al. (2004, AJ, 128, 1501) is available as the HEASARC CLASXS table.
CLSCAT Catalog
The COSMOS-Legacy survey is a 4.6-Ms Chandra program that has imaged 2.2
deg2 of the COSMOS field with an effective exposure of ~160 ks over the
central 1.5 deg2 and of ~80 ks in the remaining area. The survey is the
combination of 56 new observations obtained as an X-ray Visionary Project
with the previous C-COSMOS survey. In the reference paper, the authors
describe the reduction and analysis of the new observations and the
properties of 2273 point sources detected above a spurious probability of 2 x
10-5. The authors also present the updated properties of the C-COSMOS
sources detected in the new data. The whole survey includes 4,016 point
sources (3,814, 2,920 and 2,440 in the full, soft, and hard band). The
limiting depths are 2.2 x 10-16, 1.5 x 10-15, and 8.9 x 10-16
erg/cm2/s in the 0.5-2, 2-10, and 0.5-10 keV bands, respectively. The
observed fraction of obscured active galactic nuclei with a column density >
1022 cm-2 from the hardness ratio (HR) is ~ 50+17_-16_%. Given the
large sample, the authors compute source number counts in the hard and soft
bands, significantly reducing the uncertainties of 5% - 10%. For the first
time, they compute number counts for obscured (HR > -0.2) and unobscured (HR
< -0.2) sources and find significant differences between the two populations
in the soft band. Due to the unprecedented large exposure, the COSMOS-Legacy
area is three times larger than surveys at similar depths and its depth is
three times fainter than surveys covering similar areas. The area-flux region
occupied by COSMOS-Legacy is likely to remain unsurpassed for years to come.
The half-a-field shift tiling strategy was designed to uniformly cover the
COSMOS Hubble area in depth and point-spread function (PSF) size by combining
the old C-COSMOS (Elvis et al., 2009, ApJS, 184, 158) observations with the
new Chandra ones (see Figure 1 in the reference paper). The main properties
of the new ACIS-I Chandra COSMOS-Legacy observations are summarized in Table
1 therein. The observations took place in four blocks: 2012 November to 2013
January; 2013 March to July; 2013 October to 2014 January; and 2014 March.
The mean net effective exposure time per field was 48.8 ks after all the
cleaning and reduction operations.
COSXFIRMWC Catalog
The coeval AGN and galaxy evolution and the observed local relations between
super-massive black holes (SMBHs) and galaxy properties suggest some
connection or feedback between SMBH growth and galaxy build-up. The authors
looked for correlations between properties of X-ray detected AGN and their
far-infrared (FIR) detected host galaxies, to find quantitative evidences for
this connection, highly debated in recent years. They exploit the rich
multi-wavelength data set (from X-ray to FIR) that is available in the COSMOS
field for a large sample (692 sources) of AGN and their hosts, in the
redshift range 0.1 < z < 4, and use X-ray data to select AGN and determine
their properties (intrinsic luminosity and nuclear obscuration), and
broad-band (from UV to FIR) spectral energy distribution (SED) fitting to
derive host galaxy properties, viz., the stellar mass (M*) and the star
formation rate (SFR). The authors find that the AGN 2-10 keV luminosity
(LX) and the host galaxy 8-1000 um star formation luminosity (LSFIR)
are significantly correlated. However, the average host LSFIR has a flat
distribution in bins of AGN LX, while the average AGN LX increases in
bins of host LSFIR, with a logarithmic slope of ~ 0.7, in the redshifts
range 0.4 < z < 1.2. In the reference paper, the authors also discuss the
comparison between the distribution of these two quantities and the
predictions from hydrodynamical simulations. Finally, they find that the
average column density (NH) shows a positive correlation with the host
M*, at all redshifts, but not with the SFR (or LSFIR). This translates
into a negative correlation with specific SFR. These results are in agreement
with the idea that BH accretion and SFRs are correlated, but occur with
different variability time scales. The presence of a positive correlation
between NH and host M* suggests that the X-ray NH is not entirely due
to the circumnuclear obscuring torus, but may also include a contribution
from the host galaxy.
This table summarizes the multiwavelength properties of the 692 AGN-host
systems detected in the COSMOS field both in the X-ray and in the FIR (the
X-FIR sample).
COUP Catalog
The Chandra Orion Ultradeep Project (COUP) was a deep observation of the
Orion Nebula Cluster (ONC) that was obtained with the Chandra X-Ray
Observatory's Advanced CCD Imaging Spectrometer (ACIS). This Browse table
contains the COUP catalog of more than 1600 X-ray point sources that were
detected in the exceptionally deep 2003 January observation, which was an 838
ks exposure made over a continuous period of 13.2 days. The COUP observation
provides the most uniform and comprehensive data set on the X-ray emission of
normal stars ever obtained in the history of X-ray astronomy.
CR261CXO Catalog
This table contains some of the results from the first X-ray study of
Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open
clusters known in the Galaxy. This observation with the Chandra X-Ray
Observatory was aimed at uncovering the close interacting binaries in Cr 261,
and reached a limiting X-ray luminosity of LX ~ 4 x 1029 erg s-1 (0.3-7
keV) for stars in the cluster. The authors detected 107 sources within the
cluster half-mass radius rh, and they estimate that among the sources with
LX >~ 1030 erg s-1, about 26 are associated with the cluster. They
identify a mix of active binaries and candidate active binaries, candidate
cataclysmic variables, and stars that have "straggled" from the main locus of
CR 261 in the color-magnitude diagram. Based on a deep optical source catalog
of the field, the authors estimate that Cr 261 has an approximate mass of
6500 Msun, roughly the same as the old open cluster NGC 6791. The X-ray
emissivity of Cr 261 is similar to that of other old open clusters,
supporting the trend that they are more luminous in X-rays per unit mass than
old populations of higher (globular clusters) and lower (the local
neighborhood) stellar density. This implies that the dynamical destruction of
binaries in the densest environments is not solely responsible for the
observed differences in X-ray emissivity.
Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on
board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time
of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed
exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al.
(2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1
arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4
arcminute2) and therefore the authors placed the center of the cluster
(J2000.0 RA = 12h 38m 06.0s, Dec = -68o 22' 01" according to
Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous
part of the cluster could be imaged (see Figure 1 in the reference paper).
The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3
from the ACIS-S array. The authors limited the X-ray analysis to the data
from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3
aimpoint, giving rise to large positional errors on any sources detected on
them. Such large errors make it hard to identify optical counterparts, and
thus to classify the sources.
Source detection was done in soft (0.3-2.0 keV), hard (2-7 keV) and broad
(0.3-7 keV) energy bands. The CIAO source detection routine wavdetect was run
for eight wavelet scales ranging from 1.0 to 11.3 pixels. The wavdetect
detection threshold (sigthresh) was set at 10-7. The corresponding expected
number of spurious detections per wavelet scale is 0.42 for all four ACIS
chips combined, or 3.35 in total for all wavelet scales. The authors ran
wavdetect for the three different energy bands and then cross-correlated the
resulting source lists to obtain a master X-ray source list. They detected
113 distinct X-ray sources. To check if any real sources were missed, they
ran wavdetect again with a detection threshold of 10-6, which increased the
expected total number of spurious detections to 33.5, and found a total of
151 distinct X-ray sources with more than two counts (0.3-7 keV) in this
case. The positions of 7 of the extra 38 sources were found to match those of
short-period binaries discovered by Mazur et al. (1995, MNRAS, 273, 59; see
Section 3.4). Close, interacting binaries are plausible real X-ray sources,
and indeed the expected number of chance alignments between the Chandra
detections and the binaries in the Mazur catalog is very low, as discussed in
Section 3.5 of the reference paper. It is therefore likely that at least
these seven additional sources are real, but given the ~ 34 spurious
detections that are expected, the authors do not believe that there are many
more real sources among the extra detections. They flagged the sources that
are only found for sigthresh = 10-6, but kept them in the master source
list.
This HEASARC table contains the list of 151 X-ray sources found by wavdetect
using a detection threshold of 10-6 from Table 1 of the reference paper.
Information about the 135 optical counterparts to these X-ray sources is
available in the HEASARC table CR261OID (based on Table 2 of the reference
paper) to which this current table has links.
CR261OID Catalog
This table contains some of the results from the first X-ray study of
Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open
clusters known in the Galaxy. This observation with the Chandra X-Ray
Observatory was aimed at uncovering the close interacting binaries in Cr 261,
and reached a limiting X-ray luminosity of LX ~ 4 x 1029 erg s-1 (0.3-7
keV) for stars in the cluster. The authors detected 107 sources within the
cluster half-mass radius rh, and they estimate that among the sources with
LX >~ 1030 erg s-1, about 26 are associated with the cluster. They
identify a mix of active binaries and candidate active binaries, candidate
cataclysmic variables, and stars that have "straggled" from the main locus of
CR 261 in the color-magnitude diagram. Based on a deep optical source catalog
of the field, the authors estimate that Cr 261 has an approximate mass of
6500 Msun, roughly the same as the old open cluster NGC 6791. The X-ray
emissivity of Cr 261 is similar to that of other old open clusters,
supporting the trend that they are more luminous in X-rays per unit mass than
old populations of higher (globular clusters) and lower (the local
neighborhood) stellar density. This implies that the dynamical destruction of
binaries in the densest environments is not solely responsible for the
observed differences in X-ray emissivity.
Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on
board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time
of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed
exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al.
(2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1
arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4
arcminute2) and therefore the authors placed the center of the cluster
(J2000.0 RA = 12h 38m 06.0s, Dec = -68o 22' 01" according to
Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous
part of the cluster could be imaged (see Figure 1 in the reference paper).
The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3
from the ACIS-S array. The authors limited the X-ray analysis to the data
from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3
aimpoint, giving rise to large positional errors on any sources detected on
them. Such large errors make it hard to identify optical counterparts, and
thus to classify the sources.
The authors retrieved optical images of Cr 261 in the B and V bands from the
ESO public archive. These data were taken as part of the ESO Imaging Survey
(EIS; program ID 164.O-0561). The observations of Cr 261 were made using the
Wide Field Imager (WFI), mounted on the 2.2 m MPG/ESO telescope at La Silla,
Chile. After correcting the X-ray source positions for the (almost
negligible) boresight correction (0.06 =/- 0.07 arcseconds in RA and 0.09 +/-
0.08 arcseconds in Dec), the authors matched their X-ray source list with the
entire optical source list, using 95% match radii. For 89 unique X-ray
sources, they found 124 optical matches; of the latter, 104 are present in
both the V and B images, while for 20 there is only a V or B detection. The
authors also inspected the area around each X-ray source in the WFI images by
eye, and discovered that five more X-ray sources have candidate optical
counterparts that are saturated and therefore missing from their optical
catalog. Finally, they added to the list of candidate counterparts six
optical sources that lay just outside the 95% match radius, but inside the
3-sigma radius. In total, 98 of the 151 unique X-ray sources were thus
matched to one or more optical sources.
This HEASARC table contains the list of the 135 optical counterparts to 98 of
the 151 X-ray sources from Table 2 of the reference paper. Information about
the 151 X-ray sources is available in the HEASARC table CR261CXO (based on
Table 1 of the reference paper) to which this current table has links.
CSC Catalog
The Chandra Source Catalog (CSC) is the definitive catalog of X-ray sources
detected by the Chandra X-ray Observatory. By combining Chandra's
sub-arcsecond on-axis spatial resolution and low instrumental background with
consistent data processing, the CSC delivers a wide variety of uniformly
calibrated properties and science ready data products for detected sources
over four decades of flux. The second major release of the catalog, CSC 2.0,
includes measured properties for 317,167 unique compact and extended X-ray
sources in the sky, allowing statistical analysis of large samples, as well
as individual source studies in the "Master Sources" table, provided herein.
The extracted properties are provided for 928,280 individual observation
detections, identified in 10,382 Chandra ACIS and HRC-I imaging observations
released publicly through the end of 2014, at the
Chandra X-ray Center. CSC 2.0
includes -- as an "alpha" release -- photometric properties for 1,299 highly
extended (> ~30") sources, together with surface brightness polygons for
several contour levels.
The sensitivity limit for compact sources in CSC 2.0 is ~5 net counts (a
factor of >~2 better than the previous catalog release). This improvement is
achieved by using a two-stage approach that involves co-adding multiple
observations of the same field prior to source detection, and then using an
optimized source detection method.
For each X-ray detection and source, the catalog provides a detailed set of
more than 100 tabulated positional, spatial, photometric, spectral, and
temporal properties (each with associated lower and upper confidence
intervals and measured in multiple energy bands). The catalog Bayesian
aperture photometry code produces robust photometric probability density
functions (PDFs), even in crowded fields and for low count detections.
Release 2 uses a Bayesian Blocks analysis to identify multiple observations
of the same source that have similar photometric properties, and these are
analyzed simultaneously to improve S/N.
The energy bands used to derive many of the CSC properties are defined in
Table 4 of the reference paper: ultrasoft (u: 0.2-0.5 keV), soft (s: 0.5-1.2
keV), medium (m: 1.2-2.0 keV), hard (h: 2.0-7.0) and broad (b: 0.5-7.0 keV)
for the ACIS energy bands, and wide (w: 0.1-10.0 keV) for the HRC energy
band. The energy bands are chosen to optimize the detectability of X-ray
sources while simultaneously maximizing the discrimination between different
spectral shapes on X-ray color-color diagrams.
Numerous source-specific catalog properties are evaluated within defined
apertures. The authors define the "PSF 90% ECF aperture" for each source to
be the ellipse that encloses 90% of the total counts in a model PSF centered
on the source position. Because the size of the PSF is energy-dependent, the
dimensions of the PSF 90% ECF aperture vary with energy band. They define the
"source region aperture" for each source to be equal to the corresponding
3-sigma source region ellipse included in the merged source list, scaled by a
factor of 1.5. Like the PSF 90% ECF aperture, the source region aperture is
also centered on the source position, but the dimensions of the aperture are
independent of energy band.
CXOGSGSRC Catalog
The Chandra archival data are a valuable resource for various studies on
different X-ray astronomy topics. In this paper, the authors utilize this
wealth of information and present a uniformly processed data set, which can
be used to address a wide range of scientific questions. The data analysis
procedures are applied to 10,029 Advanced CCD Imaging Spectrometer
observations, which produces 363,530 source detections belonging to 217,828
distinct X-ray sources. This number is twice the size of the Chandra Source
Catalog (Version 1.1). The catalogs in this paper provide abundant estimates
of the detected X-ray source properties, including source positions, counts,
colors, fluxes, luminosities, variability statistics, etc.
Cross-correlation of these objects with galaxies shows that 17,828 sources
are located within the D25 isophotes of 1,110 galaxies, and 7,504 sources
are located between the D25 and 2*D25 isophotes of 910 galaxies.
Contamination analysis with the log N-log S relation indicates that 51.3% of
objects within 2*D25 isophotes are truly relevant to galaxies, and the
"net" source fraction increases to 58.9%, 67.3%, and 69.1% for sources with
luminosities above 1037, 1038, and 1039 erg/s, respectively. Among the
possible scientific uses of this catalog mentioned in this paper, the authors
discuss the possibility of studying intra-observation variability,
inter-observation variability, and supersoft sources (SSSs). About 17,092
detected sources above 10 counts are classified as variable in individual
observation with the Kolmogorov-Smirnov (K-S) criterion (PK-S < 0.01).
There are 99,647 sources observed more than once and 11,843 sources observed
10 times or more, offering a wealth of data with which to explore their
long-term variability. There are 1,638 individual objects (~2,350 detections)
classified as SSSs. As a quite interesting subclass, detailed studies on
X-ray spectra and optical spectroscopic follow-up are needed to categorize
these SSSs and pinpoint their properties. In addition, this survey can enable
a wide range of statistical studies, such as X-ray activity in different
types of stars, X-ray luminosity functions in different types of galaxies,
and multi-wavelength identification and classification of different X-ray
populations.
The ACIS observations were downloaded from the Chandra Data Archive on 2014
December 4, yielding 10,047 ACIS observations. Eighteen observations with PI
as "Calibration" or Exposure as zero were excluded. Finally, there are 10,029
ACIS observations containing 4,146 ACIS-I observations and 5,883 ACIS-S
observations in our sample. The exposure times for the selected observations
cover a range from 50 s to 190 ks, with a total of 221,851 ks.
This HEASARC table comprises the list of 218,789 X-ray point sources detected
in the Chandra ACIS Survey and listed in the machine-readable version of
Table 5 from the reference paper. This number is somewhat larger than the
number of independent sources (217,828) stated in the abstract and Section 5
of the reference paper because if a source lies within 2*R25 of more than
one galaxy it is listed multiple times, once for each galaxy with which it
may be associated. All parameters are the same for such duplicate cases
except for the entry_number, alt_name, adopted_distance, luminosity,
src_nucleus_offset, norm_src_nucleus_offset and (in some cases) source_type.
CXOXASSIST Catalog
This database table contains the latest Chandra XAssist source list. XAssist
is a NASA-funded project for the automation of X-ray astrophysics, with
emphasis on galaxies. It is capable of data reprocessing, source detection,
and preliminary spatial, temporal, and spectral analysis for all sources with
sufficient counts. The bulk of the system is written in Python, which in turn
drives underlying software, e.g., CIAO for Chandra data. Pipelines running on
Chandra observations of galaxies have generated the source list which
comprises this HEASARC table. The pipeline also includes fields requested by
users for various projects, most notably observations of a sample of quasars
and several deep field observations have been processed. Note that the
pipline processing is completely automated; therefore, users should visually
inspect the results of any queries.
CYDER Catalog
The main goal of the Calan-Yale Deep Extragalactic Research (CYDER) Survey
X-ray survey is to study serendipitous X-ray sources detected by Chandra in
an intermediate flux range (10-15 to 10-12 ergs/s) that comprises most of
the X-ray background. A total of 267 X-ray sources spread over five archived
fields were detected. The log N - log S distribution obtained for this sample
is consistent with the results of other surveys. Deep V and I images were
taken of these fields in order to calculate X-ray-to-optical flux ratios.
Identifications and redshifts were obtained for 106 sources using optical
spectroscopy from 8 m class telescopes to reach the optically faintest
sources, to the same level as deeper X-ray fields like the Chandra Deep
Fields, showing that the nature of sources detected depends mostly on the
optical limit for spectroscopy.
CYGOB2CXO Catalog
The aim of this study is to identify the so far unknown low mass stellar
population of the ~2 Myr old Cygnus OB2 star forming region, and to
investigate the X-ray and near-IR stellar properties of its members. The
authors analyzed a 97.7ks Chandra ACIS-I observation pointed at the core of
the Cygnus OB2 region. Sources were detected using the PWDETECT code and were
positionally correlated with optical and near-IR catalogs from the
literature. Source events were extracted with the ACIS EXTRACT package. X-ray
variability was characterized through the Kolmogorov-Smirnov test and spectra
were fitted using absorbed APEC thermal plasma models. The authors detected
1003 X-ray sources. Of these, 775 have near-IR counterparts and are expected
to be almost all associated with Cygnus OB2 members. From near-IR color-color
and color-magnitude diagrams, they estimate a typical absorption toward
Cygnus OB2 of AV ~ 7.0 mag. Although the region is young, very few stars (~
4.4%) show disk-induced excesses in the near-IR. X-ray variability is
detected in ~ 13% of the sources, but this fraction increases, up to 50%,
with increasing source statistics. Flares account for at least 60% of the
variability. Despite being generally bright, all but 2 of the 26 detected
O-type and early B-type stars are not significantly variable. Typical X-ray
spectral parameters are log NH ~ 22.25 (cm-2) and kT ~ 1.35 keV with
1-sigma dispersion of 0.2 dex and 0.4 keV, respectively. Variable and flaring
sources have harder spectra with median kT = 3.3 and 3.8 keV, respectively.
OB stars are typically softer (kT ~ 0.75 keV). X-ray luminosities range
between 1030 and 1031 erg s-1 for intermediate-mass and low-mass stars,
and between 2.5 x 1030 and 6.3 x 1033 erg s-1 for OB stars.
Cygnus OB2 was observed with the ACIS detector on board the Chandra
X-ray Observatory (CXO) on 2004 January 16 (Obs.Id. 4511; PI: E.
Flaccomio). The ACIS-I 17' x 17' field of view is covered by 4 chips
each with 1024 x 1024 pixels (scale 0.49 arcseconds per pixel).
The observation was pointed towards J2000.0 (RA,Dec) = (20 33 12.2,
+41 15 00.7). An SNR threshold of 4.5 sigma was chosen which resulted in
an initial source list of 1054 sources, 51 of which were subsequently rejected
as either instrumental artifacts or multiple detections of the same source
with different spatial scales. An additional 10 of the 1003 X-ray sources
in the present table are likely spurious statistical fluctuations rather
than real sources.
CYGOB2CXO2 Catalog
This table contains a catalog of 1696 X-ray sources detected in the massive
star-forming region (SFR) Cygnus OB2 and extracted from two archival Chandra
observations of the center of the region. A deep source extraction routine,
exploiting the low background rates of Chandra observations was employed to
maximize the number of sources extracted. Observations at other wavelengths
were used to identify low count-rate sources and remove likely spurious
sources. Monte Carlo simulations were also used to assess the authenticity of
these sources. X-ray spectra were fitted with thermal plasma models to
characterize the objects and X-ray light curves were analyzed to determine
their variability. The authors used a Bayesian technique to identify optical
or near-IR counterparts for 1501 (89%) of our sources, using deep
observations from the INT Photometric H-alpha Survey, the Two Micron All Sky
Survey (2MASS), and the UKIRT Infrared Deep Sky Survey-Galactic Plane Survey.
755 (45%) of these objects have six-band r', H-alpha, i', J, H, and K optical
and near-IR photometry. From an analysis of the Poisson false-source
probabilities for each source they estimate that their X-ray catalog includes
<1% of false sources, and an even lower fraction when only sources with
optical or near-IR associations are considered. A Monte Carlo simulation of
the Bayesian matching scheme allows this method to be compared to more
simplified matching techniques and enables the various sources of error to be
quantified. The catalog of 1696 objects presented here includes X-ray
broad-band fluxes, spectral model fits, and optical and near-IR photometry in
what is one of the largest X-ray catalogs of a single SFR to date. The high
number of stellar X-ray sources detected from relatively shallow observations
confirms the status and importance of Cygnus OB2 as one of our Galaxy's most
massive SFRs.
CYGTEVCXO Catalog
A 50 ks Chandra observation of the unidentified TeV source in
Cygnus reported by the High Energy Gamma-Ray Astronomy (HEGRA) collaboration
reveals no obvious diffuse X-ray counterpart. However, 240 pointlike X-ray
sources are detected within or nearby the extended TeV J2032+4130 source
region, of which at least 36 are massive stars and two may be radio emitters.
That the HEGRA source is a composite, having as a counterpart the multiple
pointlike X-ray sources that are observed, cannot be ruled out. Indeed, the
distribution of pointlike X-ray sources appears nonuniform and concentrated
broadly within the extent of the TeV source region. A hypothesis is offered
for the origin of the very high energy gamma-ray emission in Cyg OB2 based
on the local acceleration of TeV-range cosmic rays and the differential
distribution of OB versus less massive stars in this association.
The region of TeV J2032+4130 was observed by Chandra on 2004 July 12 for a
total effective exposure time of 48,728 seconds using the Advanced CCD
Imaging Specrometer imaging array (ACIS-I). The observation was centered
on J2000.0 coordinates (RA, Dec) = )20 32 07.0, +41 30 30). This table
contains the list of the 240 pointlike sources which were detected in the
ACIS-I data and their 2MASS near-IR counterparts, if any are found within
3" of the X-ray sources. 130 (54%) of the 240 X-ray sources have 2MASS
counterparts within these error radii.
ECDFSCXO Catalog
The Extended Chandra Deep Field-South (ECDFS) survey consists of
four Chandra X-Ray Observatory (CXO) ACIS-I pointings and covers ~1100
arcmin2 (~0.3 deg2) centered on the original CDF-S field to a depth of
approximately 228 ks. This is the largest Chandra survey ever conducted
at such depth, and only one XMM-Newton survey reaches a lower flux
limit in the hard 2.0-8.0 keV band. The authors detect 651 unique sources: 587
using a conservative source-detection threshold (identified by source_type =
'P' for primary source) and 64 (identified by source_type =
'S' for secondary source) using a lower
source-detection threshold. These are combined in this HEASARC representation
but were presented as two separate catalogs (Table 4 contained the primary
sources, and Table 5 the secondary sources) in the original reference paper.
Of the 651 total sources, 561 are detected in the full 0.5-8.0 keV band, 529
in the soft 0.5-2.0 keV band, and 335 in the hard 2.0-8.0 keV band. For point
sources near the aim point, the limiting fluxes are approximately
1.7 x 10-16 and 3.9 x 10-16 ergs/cm2/s in the 0.5-2.0 and 2.0-8.0 keV
bands, respectively. In their paper, the authors present the differential and
cumulative flux distributions, which are in good agreement with the number
counts from previous deep X-ray surveys and with the predictions from an
active galactic nucleus (AGN) population synthesis model that can explain the
X-ray background. In general, fainter sources have harder X-ray
spectra, consistent with the hypothesis that these sources are mainly
obscured AGNs.
All nine observations of the ECDFS survey field were conducted with
the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra as part
of the approved guest observer program in Cycle 5.
Notice that Lehmer et al. (2005, ApJS, 161, 21) conducted a somewhat
different analysis on these same data and obtained similar, but not
identical results, e.g., Lehmer et al. found 809 total X-ray sources compared
to 651 in the present table.
ECDFSNEW Catalog
This table contains the improved point-source catalog for the 250-ks Extended
Chandra Deep Field-South (E-CDF-S) Survey, implementing a number of recent
improvements in Chandra source-cataloguing methodology. For the E-CDF-S, the
main catalog (entries from which are indicated with parameter values of
source_sample = "Main" in this HEASARC representation) contains 1003 X-ray
sources detected with wavdetect at a false-positive probability threshold of
10-5 that also satisfy a binomial-probability source-selection criterion of
P < 0.002. Such an approach maximizes the number of reliable sources
detected: a total of 275 main-catalog sources are new compared to the Lehmer
et al. (2005, ApJS, 161, 21) E-CDF-S main catalog. The authors also provide
an E-CDF-S supplementary catalog that consists of 56 sources (entries from
which are indicated with parameter values of source_sample = "Supp" in this
HEASARC representation) detected at the same wavdetect threshold and having P
of 0.002-0.1 and Ks <= 22.3 mag counterparts. For all 1059 E-CDF-S sources,
including the 318 newly detected ones (these being generally fainter and more
obscured), the authors determine X-ray source positions utilizing centroid
and matched-filter techniques; they also provide multi-wavelength
identifications, apparent magnitudes of counterparts, spectroscopic and/or
photometric redshifts, basic source classifications, and estimates of
observed active galactic nucleus and galaxy source densities around
respective field centers. Simulations show that the E-CDF-S main catalog is
highly reliable and reasonably complete. Background and sensitivity analyses
indicate that the on-axis mean flux limits reached represent a factor of
~1.5-2.0 improvement over the previous E-CDF-S limit.
The 250-ks E-CDF-S is composed of four distinct and contiguous ~ 250-ks
Chandra pointings that flank the CDF-S proper, consisting of a total of nine
separate observations taken between 2004 February 29 and November 20 (see
Lehmer et al., 2005, ApJS, 161, 21 for more details).
ECDFSOID Catalog
This table contains the first results of the authors' optical
spectroscopy program aimed to provide redshifts and identifications for the
X-ray sources in the Extended Chandra Deep Field South (ECDFS). A total of
339 sources (listed herein) were targeted using the IMACS spectrograph at the
Magellan telescopes and the VIMOS spectrograph at the VLT. The authors have
measured redshifts for 186 X-ray sources, including archival data and a
literature search. They find that the active galactic nucleus (AGN) host
galaxies have on average redder rest-frame optical colors than nonactive
galaxies, and that they live mostly in the "green valley." The dependence of
the fraction of AGNs that are obscured on both luminosity and redshift is
confirmed at high significance and the observed AGN spatial density is
compared with the expectations from existing luminosity functions. These AGNs
show a significant difference in the mid-IR to X-ray flux ratio for obscured
and unobscured AGNs, which can be explained by the effects of dust
self-absorption on the former. This difference is larger for lower luminosity
sources, which is consistent with the dust opening angle depending on
AGN luminosity.
ECDFSOID2 Catalog
This table contains the results of a program to acquire
high-quality optical spectra of X-ray sources detected in the Extended-Chandra
Deep Field-South (E-CDF-S) and its central 2 Ms area. New spectroscopic
redshifts, up to z = 4, are measured for 283 counterparts to Chandra sources
with deep exposures (t ~ 2-9 hr per pointing) using multi-slit facilities on
both VLT (VIMOS) and Keck (DEIMOS), thus bringing the total number of
spectroscopically identified X-ray sources to over 500 in this survey field.
Since their new spectroscopic identifications are mainly associated with X-ray
sources in the shallower 250 ks coverage, the authors provide a comprehensive
catalog of X-ray sources detected in the E-CDF-S including the optical and
near-infrared counterparts, determined by a likelihood routine, and redshifts
(both spectroscopic and photometric), that incorporate published spectroscopic
catalogs, thus resulting in a final sample with a high fraction (80%) of X-ray
sources having secure identifications. The authors demonstrate the remarkable
coverage of the luminosity-redshift plane now accessible from their data while
emphasizing the detection of active galactic nuclei (AGNs) that contribute to
the faint end of the luminosity function (L0.5-8keV ~ 1043 - 1044 erg
s-1) at 1.5 <~ z <~ 3, including those with and without broad emission lines.
This redshift catalog includes 17 type-2 QSOs at 1 <~ z <~ 3.5 that
significantly increases (doubles) such samples. Based on thei deepest (9 hr)
VLT/VIMOS observation, the authors identify "elusive" optically faint galaxies
(Rmag ~ 25) at z ~ 2 - 3 based upon the detection of interstellar absorption
lines (e.g., O II+Si IV, C II], C IV); in their paper, they highlight one such
case, an absorption-line galaxy at z = 3.208 having no obvious signs of an AGN
in its optical spectrum. In addition, they determine accurate distances to
eight galaxy groups with extended X-ray emission detected both by Chandra and
XMM-Newton.
ECDFSRSSAM Catalog
In order to trace the instantaneous star formation rate (SFR) at high
redshift, and thus help in understanding the relation between the different
emission mechanisms related to star formation, the authors have combined the
recent 4-Ms Chandra X-ray data and the deep Very Large Array radio data in
the Extended Chandra Deep Field-South (E-CDF-S) region. They find 268 sources
detected both in the X-ray and radio bands. The availability of redshifts for
~ 95% of the sources in their sample allows them to derive reliable
luminosity estimates and the intrinsic properties from X-ray analysis for the
majority of the objects. The present table lists the X-ray properties and
redshifts of these 268 radio-selected sources.
In the E-CDF-S area, the authors have two sets of X-ray data obtained with
Chandra. The most important is a 4-Ms exposure observation resulting from the
co-addition of 54 individual Chandra ACIS-I exposures from 1999 October to
2010 July, with centers spaced within a few arcseconds of RA = 03:32:28.80,
Dec = -27:48:23 (J2000). The authors use the data from the new VLA program
which provides deep, high-resolution 1.4-GHz imaging across the full E-CDF-S,
consisting of a six-pointing mosaic of 240 h spanning 48 d of individual 5-h
observations (Miller et al., 2008, ApJS, 179, 114). The E-CDF-S area has been
targeted by a large number of spectroscopic surveys. For the X-ray sources,
the authors use the spectroscopic redshifts published in Xue et al. (2011,
ApJS, 195, 10).
ELAISCXO Catalog
This table contains the results of an analysis of two deep (75 ks)
Chandra observations of the European Large Area Infrared Space Observatory
(ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep
X-ray survey. This survey is being conducted in well-studied regions with
extensive multiwavelength coverage. This table contains the Chandra source
catalogs along with an analysis of source counts and hardness ratios.
A total of 233 X-ray point sources were detected in addition to two soft
extended sources (not included in this table of point sources), which are
found to be associated with galaxy clusters. An overdensity of sources is
found in N1 with 30 per cent more sources than N2, which the authors attribute
to large-scale structure. A similar variance is seen between other deep
Chandra surveys. The source count statistics reveal an increasing
fraction of hard sources at fainter fluxes. The number of galaxy-like
counterparts also increases dramatically towards fainter fluxes,
consistent with the emergence of a large population of obscured sources.
The ELAIS Deep X-ray Survey (EDXS) is being conducted in the northern
ELAIS regions N1 and N2. The Chandra data consist of approximately 75
ks exposures in each field. Region N1 was observed on 2000 August 3-4
(Obs_ID 888) and N2 on 2000 August 2-3 (Obs_ID 887). The nominal
aimpoints were 16:10:20.11 +54:33:22.3 for N1, and 16:36:46.99 +41:01:33.7
for N2 in J2000.0 coordinates. The ACIS-I chips were used with the
addition of the ACIS-S2 and ACIS-S4 chips.
ETGALCXO Catalog
This table contains the results of a Chandra survey of low-mass X-ray
binaries (LMXBs) in 24 early-type galaxies. Correcting for detection
incompleteness, the X-ray luminosity function (XLF) of each galaxy is
consistent with a power law with negative logarithmic differential slope,
Beta, ~ 2.0. However, Beta strongly correlates with incompleteness,
indicating the XLF flattens at low X-ray luminosity (LX). The composite XLF
is well fitted by a power law with a break at (2.21 [+0.65,-0.56]) x 1038
erg s-1 and Beta = 1.40 [+0.10,-0.13] and = 2.84 [+0.39,-0.30] below and
above it, respectively. The break is close to the Eddington limit for a 1.4
solar-mass neutron star, but the XLF shape rules out its representing the
division between neutron star and black hole systems. Although the XLFs are
similar, the authors find evidence of some variation between galaxies. The
high-LX XLF slope does not correlate with age, but may correlate with
[Alpha/Fe]. Considering only LMXBs with LX > 1037 erg s-1, matching the
LMXBs with globular clusters (GCs) identified in HST observations of 19 of
the galaxies, the authors find the probability a GC hosts an LMXB is
proportional to LGCAlpha ZFeGamma where Alpha = 1.01 +/- 0.19 and
Gamma = 0.33 +/- 0.11. Correcting for GC luminosity and color effects, and
detection incompleteness, they find no evidence that the fraction of LMXBs
with LX > 1037 erg s-1 in GCs (40%), or the fraction of GCs hosting
LMXBs (~ 6.5%) varies between galaxies. The spatial distribution of LMXBs
resembles that of GCs, and the specific frequency of LMXBs is proportional to
the GC specific luminosity, consistent with the hypothesis that all LMXBs
form in GCs. If the LMXB lifetime is TauL and the duty cycle is Fd, their
results imply ~ 1.5(TauL/108 yr)-1 Fd-1 LMXBs are formed per
gigayear per GC, and they place an upper limit of one active LMXB in the
field per 3.4 x 109 solar luminosities of V-band luminosity.
This table contains 1194 X-ray point sources that were detected within the
B-band 25th magnitude ellipse D25 (as listed in the de Vaucouleurs et al.
Catalog of Bright Galaxies) of 24 early-type galaxies observed by Chandra
(listed in Table 1 of the reference paper). The D25 restriction should
mitigate against contamination by background AGNs.
FORNAXACXO Catalog
This table contains some of the results from a Chandra ACIS sub-arcsecond
resolution X-ray observation of the archetypal merger radio galaxy NGC 1316
(Fornax A). The authors detect 81 point sources within the 25th magnitude
isophotal ellipse D25 of NGC 1316 (LX in the range of 2 x 1037 to 8 x
1039 ergs s-1), with hard (kT ~ 5 keV) X-ray spectra, typical of X-ray
binaries, and a spatial radial distribution consistent with that of the
optical (i.e., stellar) surface brightness. In the reference paper, they
derive the X-ray luminosity function (XLF) of these sources, correcting for
the incompleteness at the faint end caused by the presence of the diffuse
emission from the hot ISM in the central regions of NGC 1316 and by the
widening of the Chandra point-spread functions at increasing distance from
the aim point. With these corrections, the XLF is well reproduced by a single
unbroken power law with a slope of -1.3 down to their threshold luminosity of
~ 3 x 1037 ergs s-1.
NGC 1316 was observed for 30 ks on 2001 April 17 (ObsID 2022), with the
Chandra Advanced CCD Imaging Spectrometer (ACIS). The authors used the
back-illuminated (BI) CCD S3 (CCD ID 7) because of its sensitivity at low
energies. To include NGC 1317 (6.3 arcminutes away from NGC 1316) in the same
S3 chip, a small offset was applied to the SIM (Science Instrument Module)
position. NGC 1316 was kept close to on-axis to achieve the best spatial
resolution.
To detect X-ray sources, the authors used WAVDETECT, a wavelet detection
algorithm available in CIAO. They set the WAVDETECT significance threshold
parameter to be 10-6, which corresponds to 1 possibly spurious source, and
the scale parameter to cover seven steps between 1 and 64 pixels. This made
them sensitive to sources ranging from point-like to 32 arcseconds in size,
and in particular accommodates the variation of the point-spread function
(PSF) as a function of the off-axis angle of the sources. To extract source
properties (such as count rates, spectra, etc.), the authors used the 95%
encircled energy (at 1.5 keV) radius centered at the WAVDETECT centroid, with
a minimum of 3 arcseconds to accommodate the radial variation of he PSF.
Background counts were determined locally for each source from an annulus
from 2 to 5 times the source radius, after excluding nearby sources. Extended
sources were found at the locations of NGC 1316 and NGC 1317. In addition,
the Chandra observations reveal 94 sources (the HEASARC notes that 95 are
contained in this table), 83 of them in CCD S3. Of these, 81 sources (77 in
S3 and 4 in S2) are within the D25 ellipse. The source density increases
toward the center of NGC 1316, indicating that most of them are related to
NGC 1316. Three sources are found within the D25 ellipse of NGC 1317, with
the brightest, extended one at the center of NGC 1317. The list of detected
sources also includes sources found on CCDs other than S3 (CCD number 7).
After correcting for effective exposure and vignetting, the X-ray flux in the
0.3 - 8.0 keV band is calculated with an energy conversion factor (ECF)
assuming a power-law source spectrum with a slope of 1.7 and NH = 3 x
1020 cm-2; ECF = 6.037 x 10-12 erg cm-2 s-1 ergs per 1 count s-1
for the back-illuminated (BI) chips and 9.767 x 10-12 ergs per 1 count
s-1 for the front-illuminated (FI) CCD chips. With the adopted distance of
18.6 Mpc, the X-ray luminosities of the point sources range from ~ 2 x 1037
to ~ 8 x 1039 erg s-1.
GALCCXONID Catalog
This table contains a catalog of 5184 candidate infrared counterparts to
X-ray sources detected toward the Galactic center. The X-ray sample contains
9017 point sources detected in this region by the Chandra X-ray Observatory
during the past decade, including data from a recent deep survey of the
central 2 degrees x 0.8 degrees of the Galactic plane. A total of 6760 of
these sources have hard X-ray colors, and the majority of them lie near the
Galactic center, while most of the remaining 2257 soft X-ray sources lie in
the foreground. The authors have cross-correlated the X-ray source positions
with the 2MASS and SIRIUS near-infrared catalogs, which collectively contain
stars with a 10-sigma limiting flux of Ks <= 15.6 mag. In order to
distinguish absorbed infrared sources near the Galactic center from those in
the foreground, they defined red and blue sources as those which have H -
Ks >= 0.9 and < 0.9 mag, respectively. The authors find that 5.8% =/- 1.5%
(2 sigma) of the hard X-ray sources have real infrared counterparts, of which
228 +/- 99 are red and 166 +/- 27 are blue. The red counterparts are probably
comprised of Wolf-Rayet and O stars, high-mass X-ray binaries, and symbiotic
binaries located near the Galactic center. Foreground X-ray binaries
suffering intrinsic X-ray absorption could be included in the sample of blue
infrared counterparts to hard X-ray sources. The authors also find that 39.4%
+/- 1.0% of the soft X-ray sources have blue infrared counterparts; most of
these are probably coronally active dwarfs in the foreground. There is a
noteworthy collection of ~20 red counterparts to hard X-ray sources near the
Sagittarius B H II region, which are probably massive binaries that have
formed within the last several Myr. For each of the infrared matches to X-ray
sources in their catalog, the authors derived the probability that the
association is real, based on the source properties and the results of the
cross-correlation analysis. These data are included in this catalog and will
serve spectroscopic surveys to identify infrared counterparts to X-ray
sources near the Galactic center.
GALCENCXO Catalog
This table contains a catalog of 9017 X-ray sources identified in
Chandra observations of a 2 degrees by 0.8 degrees field around the Galactic
center. This enlarges the number of known X-ray sources in the region by a
factor of 2.5. The catalog incorporates all of the ACIS-I observations as of
2007 August, which total 2.25 Ms of exposure. At the distance to the Galactic
center (8 kpc), we are sensitive to sources with luminosities of 4 x 1032
erg s-1 (0.5-8.0 keV; 90% confidence) over an area of 1 degree2, and up to
an order of magnitude more sensitive in the deepest exposure (1.0 Ms) around
Sgr A*. The positions of 60% of the sources are accurate to <1 arcsecond (95%
confidence), and 20% have positions accurate to <0.5 arcsec. The authors
search for variable sources, and find that 3% exhibit flux variations within
an observation, and 10% exhibit variations from observation-to-observation.
They also find one source, CXOUGC J174622.7-285218, with a periodic 1745 s
signal (1.4% chance probability), which is probably a magnetically accreting
cataclysmic variable. The authors compare the spatial distribution of X-ray
sources to a model for the stellar distribution, and find 2.8 sigma evidence
for excesses in the numbers of X-ray sources in the region of recent star
formation encompassed by the Arches, Quintuplet, and Galactic center star
clusters. These excess sources are also seen in the luminosity distribution
of the X-ray sources, which is flatter near the Arches and Quintuplet than
elsewhere in the field. These excess point sources, along with a similar
longitudinal asymmetry in the distribution of diffuse iron emission that has
been reported by other authors, probably have their origin in the young stars
that are prominent at a galactic lonitude ~ 0.1 degrees.
This tables was designed to be inclusive, so sources of questionable quality
are included, according to the authors. For instance, 134 sources have net
numbers of counts in the 0.5-8.0 keV band that are consistent with 0 at the
90% confidence level. These sources are only detected in a single band and
are presumably either very hard or very soft, detected in single observations
because they were transients, or detected in stacked observations with
wvdecomp at marginal significance. The authors have chosen to
include them because they passed the test based on Poisson statistics from
Weisskopf et al. (2007, ApJ, 657, 1026).
The observations which were used to generate the source list herein tabulated
are listed in Table 1 of the reference paper.
This HEASARC table GALCENCXO supercedes and replaces the previous HEASARC
tables CHANGALCEN and CHANC150PC, which were based on Muno et al. (2003, ApJ,
589, 225) and Muno et al. (2006, ApJS, 165, 173), respectively.
GC47TUCCX2 Catalog
The authors combined Chandra ACIS observations of the globular cluster 47
Tucanae (47 Tuc) from 2000, 2002, and 2014-2015 to create a deeper X-ray
source list and study some of the faint radio millisecond pulsars (MSPs)
present in this cluster. This work combined 180 ks of new Chandra ACIS data
on 47 Tuc with 370 ks of archival data and used improved algorithms to
generate a new source catalog, finding 81 new sources for a total of 370
within the half-mass region (2.79 arcsec) of the cluster. The majority of the
newly identified sources are in the crowded core region, indicating cluster
membership. The authors associated five of the new X-ray sources with
chromospherically active BY Dra or W UMa variables identified by Albrow et
al. (2001, CDS Cat. <J/ApJ/559/1060>).
See also the related 2005 source catalog.
GC47TUCCXO Catalog
The authors have detected 300 X-ray sources within the half-mass radius
(2.79') of the globular cluster 47 Tucanae in a deep (281 ks) Chandra
exposure. They perform photometry and simple spectral fitting for our
detected sources and construct luminosity functions, X-ray color-magnitude,
and color-color diagrams. Eighty-seven X-ray sources show variability on
timescales from hours to years. Thirty-one of the new X-ray sources are
identified with chromospherically active binaries from the catalogs of Albrow
and coworkers (2001, CDS Catalog <J/ApJ/559/1060>). The authors estimate that
the total number of neutron stars in 47 Tuc is of order 300, reducing the
discrepancy between theoretical neutron star retention rates and observed
neutron star populations in globular clusters. The data used in this paper
are from the 2000 and 2002 Chandra observations of the globular cluster 47
Tuc. The 2000 observations, initially described in Grindlay et al. (2001,
Science 292, 2290), were performed with the ACIS-I CCD array at the telescope
focus, while the 2002 observations placed the back-illuminated ACIS-S aim
point at the focus for maximum low-energy sensitivity.
The authors combined the results from wavdetect source detection runs with a
threshold probability of 1 x 10-5, in two energy bands (0.5 - 2.0 keV and
0.5 - 6.0 keV for the 2000 observations, and (0.3 - 2.0 keV and 0.3 - 6.0 keV
for the 2002 observations), to make independent source lists for the 2000 and
2002 observations, given in Tables 2 and 3 of the reference paper, which have
been combined in the present HEASARC table. A total of 146 sources were
detected in this way in the 2000 observations (entries with dataset_year =
2000), while 300 sources were detected in the 2002 observations (dataset_year
= 2002). A total of 143 of the sources were clearly detected in both
observations, while only three of the sources from the 2000 observations were
not detected in the 2002 observations.
See also the related 2017 source catalog.
GCPTSRCCXO Catalog
With the superb angular resolution of the Chandra Observatory, it is now
possible to detect X-ray point sources, either embedded in galaxy clusters or
along the cluster line of sight, which could not be resolved by previous
instruments. This now allows studies of source counts in distant cluster
fields. The authors want to analyze the inner region of clusters of galaxies
to check for the presence of any over-density of X-ray point sources embedded
in the gas diffuse emission. These point sources are possible AGN belonging
to the clusters and could contaminate the cluster emission. The authors used
a sample of 18 distant (0.25 < z < 1.01) galaxy clusters from the Chandra
archive to construct the log N - log S relation, in both the soft and hard
energy bands, for the X-ray point sources detected in the central cluster
region to be compared with the counts of point sources detected in similarly
deep fields without clusters.
The authors find a ~2-sigma excess of cluster region sources at the bright
end of the log N - log S distribution. The radial distribution of the
brightest X-ray point sources confirms this excess and indicates that it is
confined to the inner 0.5 Mpc of the cluster region. The results suggest the
possible existence of X-ray sources belonging to the cluster (most probably
AGN, given their 0.5-10 keV luminosity ranging from 1043 to 1044 erg
s-1): on average one every three clusters. Unlike previous studies, which
have mainly investigated the point-source population in the vicinity of the
galaxy clusters, the present study analyzes the content of point sources
within the 1 Mpc region covered by the cluster extent. This work confirms the
findings of other investigators who analyzed the central 1 Mpc region of more
massive clusters and/or groups in a similar redshift range. The X-ray source
excess found here is much smaller than the excess of radio galaxies found
recently in high-z X-ray selected clusters, possibly due to the better
sensitivity of the radio observations.
The properties of the clusters and of the Chandra exposures in which they
were observed are given in Table 1 of the reference paper, and are reproduced
below:
Cluster Name z RA (J2000) Dec ObsID ACIS Mode Exp N_H L_sb L_hb
h m s d ' " ks [units are below]
Abell 2125 0.246 15 41 12 +66 16 01 2207 I VF 79.7 2.77 0.13 0.56
ZW CL 1454.8+2233 0.258 14 57 15 +22 20 33 4192 I VF 91.4 3.22 0.23 0.74
MS 1008.1-1224 0.302 10 10 32 -12 39 23 926 I VF 44.2 6.74 0.44 1.57
ZW CL 0024.0+1652 0.394 00 26 35 +17 09 39 929 S VF 36.7 4.19 0.34 2.22
MS 1621.5+2640 0.426 16 23 36 +26 34 21 546 I F 30.0 3.59 0.81 3.41
RXJ 1701.3+6414 0.453 17 01 24 +64 14 10 547 I VF 49.5 2.59 0.64 2.67
CL 1641+4001 0.464 16 41 53 +40 01 46 3575 I VF 44.0 1.02 0.67 2.62
V 1524.6+0957 0.516 15 24 40 +09 57 48 1664 I VF 49.9 2.92 0.89 3.29
MS 0451.6-0305 0.539 04 54 12 -03 00 53 902 S F 41.5 5.18 0.73 4.12
V 1121+2327 0.562 11 20 57 +23 26 27 1660 I VF 66.9 1.30 0.73 3.00
MS 2053.7-0449 0.583 20 56 21 -04 37 51 1667 I VF 43.5 4.96 1.32 4.91
V 1221+4918 0.700 12 21 26 +49 18 30 1662 I VF 79.4 1.44 1.18 4.62
MS 1137.5+6625 0.782 11 40 22 +66 08 18 536 I VF 117.5 1.18 0.81 4.04
RDCSJ 1317+2911 0.805 13 17 21 +29 11 19 2228 I VF 111.3 1.04 0.85 3.59
RDCSJ 1350+6007 0.805 13 50 48 +60 06 54 2229 I VF 58.3 1.76 1.77 7.26
RXJ 1716.4+6708 0.813 17 16 49 +67 08 26 548 I F 51.5 3.71 2.17 9.45
MS 1054.4-0321 0.830 10 56 59 -03 37 37 512 S F 67.5 3.67 1.07 6.61
WARPJ 1415.1+3612 1.013 14 15 11 +36 12 00 4163 I VF 89.2 1.10 1.93 7.54
where Exp is the Chandra exposure time in ks corresponding to the nominal
exposure filtered to exclude time periods of high background, N_H is the
Galactic hydrogen column density in the direction of the cluster of galaxies,
in units of 1020 cm-2, and L_sb and L_hb are the limiting luminosities in
units of 1042 erg s-1 for point sources in the clusters in the 0.5-2.0
keV and 2-10 keV energy bands, respectively.
GWSSTRPCXO Catalog
This table contains the optical and X-ray spectral properties of the sources
detected in a 200-ks Chandra observation of part of the Groth-Westphal Strip
(GWS) region, using the ACIS-I instrument. The authors present a relatively
simple method for the detection of X-ray point sources and the calculation of
limiting sensitivities, which they argue is at least as sensitive and more
self-consistent than previous methods presented in the literature. A total of
158 distinct X-ray sources are included in this point-source catalogue in the
ACIS-I area with a threshold Poisson detection probability of 4 x 10-6. The
number counts show a relative dearth of X-ray sources in this region.
A wealth of optical photometric and spectroscopic data are available in this
field providing optical identifications and redshift determinations for the
X-ray population. The optical photometry and spectroscopy used here are
primarily from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey
with additional redshifts obtained from the literature. These are
complemented with the deeper (r ~ 26 mag) multiwaveband data (ugriz) from the
Canada-France-Hawaii Telescope Legacy Survey to estimate photometric
redshifts and to optically identify sources fainter than the DEEP2 magnitude
limit (RAB ~ 24.5 mag). The authors focus their study on the 2 - 10 keV
selected sample comprising 97 sources to the flux limit ~8 x 10-16
erg/s/cm2, this being the most complete in terms of optical identification
rate (86 per cent) and redshift determination fraction (63 per cent; both
spectroscopic and photometric).
Chandra observed the GWS, which is part of the Extended Groth Strip (EGS)
region, on three separate occasions between 2002 August 11 and 22, using
ACIS-I as the prime instrument. The S2 and S3 chips of the ACIS-S array were
also operating during the observation, but as these are far off-axis their
data are not considered further. The sequence number identifying the
observations was 900144 and the three observation ID numbers (3305 on
2002-08-11, 4357 on 2002-08-12, and 4365 on 2002-08-21).
HCGXRBS Catalog
This catalog presents the study of a sample of 15 compact groups (CGs)
observed with Chandra/ACIS, Swift/UVOT and Spitzer/IRAC-MIPS for which
archival data exist, allowing the authors to obtain SFRs, stellar masses,
sSFRs and X-ray fluxes and luminosities for individual, off-nuclear point
sources, which they summed to obtain total X-ray luminosities originating in
off-nuclear point sources in a galaxy.
Details on the Swift and Spitzer observations and data for systems in this
sample can be found in Tzanavaris et al. (2010ApJ...716..556T) and Lenkic et
al. (2016MNRAS.459.2948L). For Chandra/ACIS observations, see Tzanavaris et
al. (2014ApJS..212....9T) and Desjardins et al. (2013ApJ...763..121D;
2014ApJ...790..132D).
The authors obtained total galaxy X-ray luminosities, LX, originating from
individually detected point sources in a sample of 47 galaxies in 15 compact
groups of galaxies (CGs). For the great majority of the galaxies, they found
that the detected point sources most likely are local to their associated
galaxy, and are thus extragalactic X-ray binaries (XRBs) or nuclear active
galactic nuclei (AGNs). For spiral and irregular galaxies, they found that,
after accounting for AGNs and nuclear sources, most CG galaxies are either
within the +/- 1 sigma scatter of the Mineo et al. LX-star formation rate
(SFR) correlation or have higher LX than predicted by this correlation for
their SFR. These "excesses" may be due to low metallicities and high
interaction levels. For elliptical and S0 galaxies, after accounting for AGNs
and nuclear sources, most CG galaxies were found to be consistent with the
Boroson et al. LX-stellar mass correlation for low-mass XRBs, with larger
scatter, likely due to residual effects such as AGN activity or hot gas.
Assuming non-nuclear sources are low- or high-mass XRBs, the authors used
appropriate XRB luminosity functions to estimate the probability that
stochastic effects can lead to such extreme LX values. They found that,
although stochastic effects do not in general appear to be important, for
some galaxies there is a significant probability that high LX values can be
observed due to strong XRB variability.
HPERSEICXO Catalog
This table contains some of the results from a Chandra/ACIS-I observations of
the massive ~ 13-14 Myr-old cluster, h Persei, part of the famous Double
Cluster (h and Chi Persei) in Perseus. Combining the list of 330
Chandra-detected sources with new optical/IR photometry and optical
spectroscopy reveals ~ 165 X-ray bright stars with V <~ 23. Roughly 142 have
optical magnitudes and colors consistent with cluster membership. The
observed distribution of X-ray luminosity Lx peaks at Lx ~ 1030.3 erg
s-1 and likely traces the bright edge of a far larger population of ~ 0.4-2
Msun X-ray active stars. From a short list of X-ray active stars with IRAC
8-micron excess from warm, terrestrial zone dust, the authors derive a
maximum X-ray flux incident on forming terrestrial planets. Although there is
no correlation between X-ray activity and IRAC excess, the fractional X-ray
luminosity correlates with optical colors and spectral type. By comparing the
distribution of Lx/Lstar versus spectral type and (V-I) in h Per with
results for other 1-100 Myr-old clusters, the authors show that stars
slightly more massive than the Sun (>~ 1.5 Msun) fall out of X-ray
saturation by ~ 10-15 Myr. Changes in stellar structure for >~ 1.5 Msun
stars likely play an important role in this decline of X-ray emission.
Chandra observations of h Persei were taken with a 41.1 ks exposure on 2004
December 2, (Obs. ID 5407; Sequence Number 200341) with the ACIS detector
(chips 0, 1, 2, 3, 6, and 7). The data were obtained in dithered, timed mode,
with a frametime of 3.2 s. On-board event rejection and event telemetry was
in the VFAINT mode. The field was centered on RA(2000) = 2h19m00s, Dec(2000)
= 57d07'12", close to the center of h Persei from Bragg & Kenyon (2005, AJ,
130, 134) (RA(2000) = 2h18m56.4s, Dec(2000) = 57d08'25") and observed at a
roll angle of 229 degrees. The data were not registered to an astrometric
reference frame (e.g., Two Micron All Sky Survey, 2MASS). The ACIS-I field
covers a 17' x 17' area.
IC10CXO Catalog
The authors monitored the Cassiopeia dwarf galaxy (IC 10) in a series of 10
Chandra ACIS-S observations to capture its variable and transient X-ray
source population, which is expected to be dominated by High Mass X-ray
Binaries (HMXBs). They present a sample of 21 X-ray sources that are variable
between observations at the 3-sigma level, from a catalog of 110 unique point
sources (the HEASARC notes that there are actually 111 sources in the CDS
version of the catalog from which this HEASARC table originates). The authors
find four transients (flux variability ratio greater than 10) and a further
eight objects with ratios >5. The observations span the years 2003-2010 and
reach a limiting luminosity of >1035 erg/s, providing sensitivity to X-ray
binaries in IC 10 as well as flare stars in the foreground Milky Way. The
nature of the variable sources is investigated from light curves, X-ray
spectra, energy quantiles, and optical counterparts. The purpose of this
study is to discover the composition of the X-ray binary population in a
young starburst environment. IC 10 provides a sharp contrast in stellar
population age (<10 million years) when compared to the Magellanic Clouds
(40-200 Myr) where most of the known HMXBs reside. The authors find 10 strong
HMXB candidates, 2 probable background active galactic nuclei, 4 foreground
flare-stars or active binaries, and 5 not yet classifiable sources. Complete
classification of the sample requires optical spectroscopy for radial
velocity analysis and deeper X-ray observations to obtain higher S/N spectra
and search for pulsations. A catalog (contained in this HEASARC table) has
been created and supporting data sets (the data used to create the light
curves shown in Figures 3, 4 and 5 in the reference paper) are available at
http://cdsarc.u-strasbg.fr/ftp/cats/J/ApJ/836/50/.
A monitoring series of 7x15 ks Chandra/ACIS observations, spaced at roughly
six-week intervals was obtained during 2009-2010. A pair of very deep ACIS-S3
observations (2x45ks) made in 2006 November provided a reference data set for
improved source positions and spectral information. The original Wang+ (2005,
MNRAS, 362, 1065) Chandra (ACIS-S3) observation of 30 ks made in 2003 was
also included in this analysis.
The complete listing of 10 Chandra observation identifiers (ObsIDs)
comprising the data set is summarized in Table 1 of the reference paper, also
shown here:
MJD |Date |ObsID|Flag|Exp.|RA(J2000)Dec(J2000)|Roll|Num. Sources
ks hh mm ss dd mm ss deg.
52710.7|2003 Mar 12 |03953|a |28.9|00 20 25 +59 16 55|339.27|31
54041.8|2006 Nov 2 |07082| |40.1|00 20 04 +59 16 45|223.70|48
54044.2|2006 Nov 5 |08458| |40.5|00 20 04 +59 16 45|223.70|41
55140.7|2009 Nov 5 |11080| |14.6|00 20 17 +59 17 56|226.53|19
55190.2|2009 Dec 25 |11081| | 8.1|00 20 19 +59 18 02|286.15|24
55238.5|2010 Feb 11 |11082| |14.7|00 20 23 +59 17 10|320.56|24
55290.6|2010 Apr 4 |11083| |14.7|00 20 34 +59 19 01| 10.32|25
55337.8|2010 May 21 |11084| |14.2|00 20 25 +59 20 16| 67.89|27
55397.5|2010 Jul 20 |11085| |14.5|00 20 11 +59 19 13|121.25|22
55444.6|2010 Sep 5 |11086| |14.7|00 20 15 +59 18 11|157.71|27
|2006 Nov 2-5 |57082|b |80.6|00 20 04 +59 16 45|223.70|63
Flag values as follows:
a = ObsID 03953 used about half of the CCD area in subarray mode.
b = Merged 2006 data set referred to as ObsID 57082 consists of the nearly
contiguous ObsIDs 07082 and 08458, which had identical pointings.
Roll is the spacecraft roll angle, and Num. Sources is the number of unique
point sources detected in each observation after combining wavdetect lists
from the soft (S: 0.3-1.5 keV), broad (B: 0.3-8 keV) and hard (H: 2.5-8 keV)
energy bands.
IC10XMMCXO Catalog
This table contains some of the results from an X-ray study of our nearest
starburst galaxy IC 10, based on XMM-Newton and Chandra observations. It
contains a list of 73 XMM-Newton and 28 Chandra detections of point-like
X-ray sources in the field of this galaxy; a substantial fraction of them are
likely to be stellar objects in the Milky Way due to the low Galactic
latitude location of IC 10. The brightest source in the IC 10 field, X-1, has
a mean 0.3-8.0 keV luminosity of ~1.2E38 erg s-1 and shows a large
variation by a factor of up to ~6 on timescales of ~104 s during the
XMM-Newton observation.
The XMM-Newton observations were taken on 2003 July 3 with a total exposure
time of ~45 ks for the EPIC-MOS cameras and ~42 ks for the European Photon
Imaging Camera (EPIC) PN camera. The authors use only the data from the PN
camera (with a thin optical blocking filter) because of its high sensitivity
to soft X-rays in the study of diffuse emission and include the data from the
MOS cameras in the analysis of X-1. The Chandra observation, taken on 2003
March 12 with an exposure of 29 ks and already described by Bauer and Brandt
(2004, ApJ, 601, 67), was reprocessed by the authors using the then-latest
CIAO software (version 3.2.1) and calibration database (version 3.0.0).
The authors used the Two-Micron All Sky Survey (2MASS) All-Sky Catalog of
Point Sources (Cutri et al. 2003 CDS Catalog II/246) to search for potential
counterparts. They cross-correlated the spatial positions of the objects in
this catalog with their X-ray source positions, using a matching radius of 4
arcsec for XMM-Newton PN sources and 2 arcsec for Chandra ACIS sources. The
radius was chosen to be greater than the 1-sigma statistical position
uncertainty of almost all the sources.In no case is there a match with
multiple 2MASS objects. The 3-sigma limiting sensitivities of the 2MASS
Catalog are 17.1, 16.4 and 15.3 mag in the three bands, J, H, and KS,
respectively.
IC1396ACXO Catalog
Rich, young stellar clusters produce H II regions whose expansion into the
nearby molecular cloud is thought to trigger the formation of new stars.
However, the importance of this mode of star formation is uncertain. This
investigation seeks to quantify triggered star formation (TSF) in IC 1396A
(aka the Elephant Trunk Nebula), a bright-rimmed cloud (BRC) on the periphery
of the nearby giant HII region IC 1396 produced by the Trumpler 37 cluster.
X-ray selection of young stars from Chandra X-ray Observatory data is
combined with existing optical and infrared surveys to give a more complete
census of the TSF population. Over 250 young stars in and around IC 1396A are
identified; this doubles the previously known population. A spatio-temporal
gradient of stars from the IC 1396A cloud towards the primary ionizing star
HD 206267 is found.
The current project consists of two Chandra-ACIS X-ray observations of IC
1396A, a Guaranteed Time observation (ObsID No. 11807 obtained on 2010 March
31; PI: Garmire) and a Guest Observer observation (ObsID No. 10990 obtained
on 2010 June 9; PI: Getman). Both observations were pointed at the head of
the globule but had different roll angles. For each observation, the authors
considered only results arising from the imaging array (ACIS-I) of four
abutted 1024 x 1024 pixel front-side illuminated charge-coupled devices
(CCDs) covering about 17 x 17 arcmin2 on the sky,
Similar to the Chandra catalog of X-ray sources in the Carina Nebula (Broos
et al. 2011, ApJS, 194, 2), this list of candidate sources in IC 1396A is
trimmed to omit sources with fewer than 3 total source counts (the sum of the
net counts and the background counts, NC + BC < 3) and the probability for
being a background fluctuation greater than 1% (prob_no_src > 0.01). The
final catalog comprises 415 X-ray sources, roughly half of which sources are
extragalactic with extremely optically faint counterparts (Section 3.2 of the
reference paper), and the rest are young stars associated with the Trumpler
37 and IC 1396A star-forming regions.
UVRc Ic observations were carried out with the 1.2-m telescope at the
Fred Lawrence Whipple Observatory (FLWO), using the 4Shooter CCD array,
between 2000 September and 2002 September. 4Shooter is an array of four CCDs,
covering a square of 25 arcminutes on the side. Two 4Shooter fields were
taken to cover an ~45 x 25 arcmin2 area centered on the star HD 206267. The
FLWO fields contain the whole ACIS field, except for a small gap in between
the four CCDs of 4Shooter. All but a few Chandra stars were observed in 2000
September. UVRJ IJ observations of Trumpler 37/IC 1396A were obtained in
service mode during three nights in 2007 June 9-11 using the wide-field
camera, LAICA, mounted on the 3.5-m telescope in Calar Alto, Spain. LAICA is
a 2 x 2 mosaic of four CCDs, each covering a 15.3 x 15.3 arcmin2 field of
view (FOV) with a large gap of 15.3 x 15.3 arcmin2 in between. The project
combines four LAICA pointings covering an ~45 x 45 arcmin2 area around HD
206267, including nearly the entire ACIS field.
The Spitzer observation was obtained on 2003 December 20 with the IRAC
detector in all four IRAC channels (3.6, 4.5, 5.8 and 8.0 micron). Two
adjacent fields subtending ~37 x 42 arcmin2 in channel pairs 3.6/5.8 micron
and 4.5/8.0 micron were centered on Trumpler 37. To reduce unnecessary data
processing the authors analyzed only a portion of the original data that
encompassed the Chandra-ACIS field with a coverage of ~19 x 19 arcmin2 area
in all four channels centered on Rim A of the IC 1396A globule. This covers
93% of the ACIS field omitting its north-western and south-western edges.
An automated cross-correlation between the Chandra source positions and the
optical-IR source positions was made using a search radius of 2 arcseconds
within ~6 arcminutes of the ACIS field center, and a search radius of 3.5
arcseconds in the outer regions of the ACIS field where the X-ray source
positions are more uncertain due to the deterioration of the Chandra telescope
PSF. This was followed by a careful visual examination of each source in both
bands to remove dubious sources and associations.
IC1396NCXO Catalog
The IC 1396N cometary globule (CG) within the large nearby HII region IC 1396
has been observed with the Advanced CCD Imaging Spectrometer (ACIS) detector
on board the Chandra X-Ray Observatory on 2004 October 16.93 to 17.30. 117
X-ray sources are detected, of which ~ 50-60 are likely members of the young
open cluster Trumpler 37 dispersed throughout the HII region, and 25 are
associated with young stars formed within the globule. Infrared photometry
(2MASS and Spitzer) shows that the X-ray population is very young: 3 older
Class III stars, 16 classical T Tauri stars, and 6 protostars including a
Class 0/I system. The authors infer a total T Tauri population of ~ 30 stars
in the globule, including the undetected population, with a star formation
efficiency of 1%-4%. An elongated source spatial distribution with an age
gradient oriented toward the exciting star is discovered in the X-ray
population of IC 1396N, supporting similar findings in other cometary
globules. The geometric and age distribution is consistent with the
radiation-driven implosion (RDI) model for triggered star formation in CGs by
H II region shocks.
The authors include only results arising from the imaging array (ACIS-I) of
four abutted 1024 x 1024 pixel front-side illuminated CCDs covering about 17'
x 17' on the sky. The aim point of the array was R.A. = 21h40m42.4s, Dec. =
+58d1609.7" (J2000.0) or (l,b) = (100.0, + 4.2), and the satellite roll angle
(i.e., orientation of the CCD array relative to the north-south direction)
was 245.9 degrees. The total net exposure time of the observation is 30 ks
with no background flaring due to solar activity or data losses.
IC348CXO Catalog
The authors have obtained a deep (53 ks) X-ray image of the very
young stellar cluster IC 348 with the Advanced CCD Imaging Spectrometer on
board the Chandra X-Ray Observatory. In this image with a sensitivity limit of
~ 1 x 10^28 ergs/s (more than 10 times deeper than their ROSAT images of IC
348), 215 X-ray sources were detected. While 115 of these sources can be
identified with known cluster members, 58 X-ray sources are most likely new,
still unidentified cluster members. About 80% of all known cluster members
with masses between ~0.15 and 2 solar masses are visible as X-ray sources
in the ACIS image. X-ray emission at levels of ~10^28 ergs/s was discovered
from four of 13 known brown dwarfs and from three of 12 brown dwarf candidates
in IC 348. X-ray emission was also detected from two deeply embedded objects,
presumably class I protostars, south of the cluster center.
Optical and infrared counterparts have been identified for most of the
X-ray sources. Some 40 X-ray sources do not have optical or IR counterparts,
and are most likely background (probably extragalactic) objects. This number
is consistent with the expected number of extragalactic background X-ray
sources based on the observed log N - log S statistics from the deep X-ray
counts in the Chandra Deep Field South.
IC348CXO2 Catalog
IC 348 is a nearby (~ 310 pc), young (~ 2 - 3 Myr) open cluster with > 300
members identified from optical and infrared observations. The authors
studied the properties of the coronae of the young low-mass stars in IC 348,
combining X-ray and optical/infrared data. The four existing Chandra
observations of IC 348 were merged, thus providing a deeper and spatially
more complete X-ray view than previous X-ray studies of the cluster. The
authors compiled a comprehensive catalog of IC 348 members taking into
account recent updates to the cluster census. Their data collection comprises
fundamental stellar parameters, infrared excess indicating the presence of
disks, H-alpha emission as a tracer of chromospheric emission or accretion,
and mass accretion rates. The authors have detected 290 X-ray sources in four
merged Chandra exposures, of which 185 are associated with known cluster
members corresponding to a detection rate of ~ 60% for the cluster members of
IC 348 identified in optical/infrared studies. According to the most recent
spectral classification of IC 348 members, only four of the X-ray sources are
brown dwarfs (spectral type M6 and later). The detection rate is highest for
diskless Class III stars and increases with stellar mass. This may be
explained with higher X-ray luminosities for higher mass and later
evolutionary stage that is evident in the X-ray luminosity functions. In
particular, the authors find that for the lowest examined masses (0.1 Msun
- 0.25 Msun) there is a difference between the X-ray luminosity functions
of accreting and non-accreting stars (classified on the basis of their
H-alpha emission strength) as well as those of disk-bearing and diskless
stars (classified on the basis of the slope of the spectral energy
distribution). These differences disappear for higher masses. This is related
to the finding that the Lx/Lbol ratio is non-constant across the
mass/luminosity sequence of IC 348 with a decrease towards lower luminosity
stars. Their analysis of an analogous stellar sample in the Orion Nebula
Cluster suggests to the authors that the decline of Lx/Lbol for young
stars at the low-mass end of the stellar sequence is likely universal.
X-ray fluxes are presented for all (185) known optical/infrared IC348 members
which were observed and detected by Chandra. The basic source parameters for
all X-ray sources, i.e., including an additional 105 sources not associated
with known IC 348 members, are given. The X-ray flux upper limits for 129 IC
348 members which were observed but not detected by Chandra (present in the
as published version of Table 3 from the reference paper) are not included in
this HEASARC representation of the data given in Tables 3 and 7 from the
reference paper. Thus, this table contains 290 (185 + 105) rows, one for each
X-ray source (IC 348 member or not) detected by Chandra in the direction of
IC 348.
IR20126CXO Catalog
This table contains results from Chandra ACIS-I and Karl G. Jansky Very Large
Array 6-cm continuum observations of the IRAS 20126+4104 massive star-forming
region. The authors detect 150 X-ray sources within the 17' x 17' ACIS-I
field, and a total of 13 radio sources within the 9.2' primary JVLA beam at
4.9 GHz. Among these observations are the first 6-cm detections of the
central sources reported by Hofner et al. (2007, A&A, 465, 197), namely,
I20N1, I20S, and I20var. A new variable radio source is also reported in
Section 3.2 of the reference paper, [MHA2015] VLA G78.1907+3.364. Searching
the 2MASS archive, the authors identified 88 near-infrared (NIR) counterparts
to the X-ray sources. Only four of the X-ray sources had 6-cm counterparts.
Based on an NIR color-color analysis and on the Besancon simulation of
Galactic stellar populations, the authors estimate that approximately 80
X-ray sources are associated with this massive star-forming region. They
detect an increasing surface density of X-ray sources toward the massive
protostar IRAS 20126+4104 and infer the presence of a cluster of at least 43
young stellar objects within a distance of 1.2 pc from this protostar.
The authors observed the IRAS 20126+4104 region with the Chandra ACIS-I
instrument on 2003 March 17 for a total exposure time of 39.35 ks. C-band (6
cm) continuum observations of the massive star-forming region IRAS 20126+4104
were conducted with the VLA operated by NRAO on 2011 August 7. These X-ray
and radio data are augmented by NIR and optical archival data. For the Mid-IR
wavelength regions, the authors searched the Spitzer Enhanced Imaging
Products Point Source catalog.
LALABOOCXO Catalog
This table contains the results of an analysis of a deep, 172 ks
Chandra observation of the Large Area Lyman Alpha survey (LALA) Bootes field
which was obtained with the Advanced CCD Imaging Spectrometer (ACIS-I) on
board the Chandra X-Ray Observatory. This is one of the deepest Chandra images
of the extragalactic sky, with only the 2 Ms Chandra Deep Field North (CDF-N)
and the 1 Ms Chandra Deep Field South (CDF-S) observations being substantially
deeper. In this table, the X-ray source catalog obtained from this image is
presented, along with some results from an analysis of the X-ray source counts
and optical identifications. The X-ray image is composed of two individual
observations obtained in 2002 and reaches 0.5 - 2.0 and 2.0 - 10.0 keV flux
limits of 1.5 x 10^-16 and 1.0 x 10^-15 ergs/cm^2/s, respectively, for
point sources near the aim point. A total of 168 X-ray sources were
detected: 160 in the 0.5 - 7.0 keV band, 132 in the 0.5 - 2.0 keV band, and
111 in the 2.0 - 7.0 keV band. Since X-ray source number 122 has two possible
optical counterparts, it is listed twice, once for each counterpart, and
the total number of entries in this table is this 169.
The primary optical data are R-band imaging from the NOAO Deep
Wide-Field Survey (NDWFS), with a limiting magnitude of R = 25.7 magnitudes,
(Vega, 3-sigma detection level, and a 4" diameter aperture). Optical
counterparts within 1.5" or the 3-sigma X-ray positional uncertainties,
whichever was larger, were detected above this level in the R band for 144
of the 168 X-ray sources. At least 90% of the optical counterparts should
be the correct matches, and, at worst, there might be ~14 false matches.
LALACETCXO Catalog
The 174 ks Chandra Advanced CCD Imaging Spectrometer (ACIS)
exposure of the Large Area Lyman Alpha Survey (LALA) Cetus field is the
second of the two deep Chandra images on LALA fields. In their paper, the
authors present the Chandra X-ray sources detected in the Cetus field, along
with an analysis of X-ray source counts, the stacked X-ray spectrum, and
the optical identifications. A total of 188 X-ray sources were detected: 174
in the 0.5-7.0 keV band, 154 in the 0.5-2.0 keV band, and 113 in the
2.0-7.0 keV band. The X-ray source counts were derived and compared
with the 172 ks exposure LALA Bootes field (available as the LALABOOCXO
table in Browse). Interestingly, the authors find consistent hard-band X-ray
source density, but a (36 +/- 12)% higher soft-band X-ray source density in
the Cetus field. The weighted stacked spectrum of the detected X-ray sources
can be fitted by a power law with photon index Gamma = 1.55. Based on the
weighted stacked spectrum, the authors find that the resolved fraction of
the X-ray background drops from (72 +/- 1)% at 0.5-1.0 keV to (63 +/- 4)%
at 6.0-8.0 keV. The unresolved spectrum can be fitted by a power law over
the range 0.5-7 keV, with a photon index Gamma = 1.22. Optical counterparts
are also presented for 154 of the X-ray sources, down to a limiting magnitude
of r' = 25.9 (Vega), using a deep r'-band image obtained with the MMT.
LKHA101CXO Catalog
This table contains some of the results from a multi-wavelength study of
a partially embedded region of star formation centered on the Herbig Be
star LkH-alpha 101. Using two 40 ks Chandra observations, The authors have
detected 213 X-ray sources in the ~ 17' x 17' ACIS-I field. They combine
the X-ray data with Two Micron All Sky Survey (2MASS) near-IR observations
and Spitzer Space Telescope (SST) IRAC and MIPS 24-micron observations to
obtain a complete picture of the cluster. A total of 158 of the X-ray sources
have infrared counterparts. Of these, the authors find nine protostars,
48 Class II objects, five transition objects, and 72 Class III objects.
From the Spitzer data, they identify an additional 10 protostars, 53 Class
II objects, and four transition disk candidates which are not detected
by Chandra. (These objects are not included in this HEASARC table which
contains the multi-wavelength data for only the 213 detected X-ray sources).
The authors obtained optical spectra of a sample of both X-ray-detected and
non-X-ray-detected objects. Combining the X-ray, Spitzer, and spectral data,
they obtain independent estimates of cluster distance and the total cluster
size - excluding protostars. The authors obtain consistent distance estimates
of 510 (+100,-40) pc and a total cluster size of 255 (+50,-25) stars. They
find the Class II:III ratio is about 5:7 with some evidence that the Class
III sources are spatially more dispersed. The cluster appears very young
with three sites of active star formation and a median age of about 1 Myr.
The field was observed by Chandra on 2005 March 6 starting at 17:16 UT for
40.2 ks of total time and 39.6 ks of the so-called good time (Chandra ObsID
5429). It was observed again on 2005 March 8 starting at 17:43 UT for
essentially the same duration (Chandra ObsID 5428). The ACIS was used in the
nominal imaging array (chips I0-I3) which provides a field of view of
approximately 17' x 17'. The aimpoint was at RA, Dec = 04:30:14.4, +35:16:22.2
(J2000.0) with a roll angle of 281 degrees. In addition, the S2 and S3 chips
were active; however, the analysis of these data is not presented here.
For purposes of point-source detection, the data from the two observations
were merged into a single event list following established CIAO procedures to
create a merged event list. To identify point sources, photons with energies
below 300 eV and above 8.0 keV were filtered out from this merged event list.
This excluded energies which generally lack a stellar contribution. By
filtering the data as described, contributions from hard, non-stellar sources
such as X-ray binaries and active galactic nuclei (AGNs) are attenuated, as is
noise. A monochromatic exposure map was generated in the standard way using an
energy of 1.49 keV which is a reasonable match to the expected peak energy of
the stellar sources and the Chandra mirror transmission. The CIAO tool
WavDetect was then run on a series of flux-corrected images binned by 1, 2,
and 4 pixels. The output source lists were combined and this resulted in the
detection of 231 sources. The authors defined false detections as any sources
with < 4 net counts or any sources more than 5' off-axis with < 7 net counts.
By this definition, 18 of the 231 detections were rejected as false detections.
A post facto check confirmed that none of these (spurious) sources had an
infrared counterpart.
LMC30DRCXO Catalog
This table contains the results of a study of the X-ray point-source
population of the 30 Doradus (30 Dor) star-forming complex in the Large
Magellanic Cloud (LMC) using high spatial-resolution X-ray images and
spatially-resolved spectra obtained with the Advanced CCD Imaging
Spectrometer (ACIS) on board the Chandra X-Ray Observatory. The observation
of ~21 ks was made on 1999 September 21 and placed the cluster R136 at the
aim point of the ACIS Imaging Array (ACIS-I). This table lists the the X-ray
sources detected in the 17' x 17' field centered on R136, the massive star
cluster which lies at the center of the main 30 Dor nebula. 20 of the 32
Wolf-Rayet stars in the ACIS field are detected. The cluster R136 is resolved
at the sub-arcsecond level into almost 100 X-ray sources, including many
typical O3-O5 stars, as well as a few bright X-ray sources which had been
previously reported. Over 2 orders of magnitude of scatter in the X-ray
luminosity Lx (calculated assuming a distance of 50 kpc) is seen among R136
O stars, suggesting that X-ray emission in the most massive stars depends
critically on the details of wind properties and the binarity of each system,
rather than reflecting the widely reported characteristic value Lx/Lbol
~ 10-7. Such a canonical ratio may exist for single massive stars in R136,
but these data are too shallow to confirm this relationship. Through this and
more recent X-ray studies of 30 Dor, the complete life cycle of a massive
stellar cluster can be revealed.
This HEASARC table contains both the primary high-significance X-ray sources
as well as some lower-significance tentative X-ray sources. The latter
sources should not be considered definitive. A subsequent Chandra observation
of this field, with several times the exposure of this observation, will
result in a longer, more complete list of point sources than that given in
this paper.
LMCN11CXO Catalog
A very sensitive X-ray investigation of the giant H II region N11
in the Large Magellanic Cloud (LMC) was performed using the Chandra X-ray
Observatory in which 165 point sources were detected. The 300-ks observation
reveals X-ray sources with luminosities (if at the 50 kpc distance of the LMC)
down to 1032 erg s-1, increasing the number of known point sources in the
field by more than a factor of five. Among these detections are 13 massive
stars (3 compact groups of massive stars, 9 O stars, and one early B star)
with log(LX/LBOL) ~ -6.5 to -7, which may suggest that they are highly
magnetic or colliding-wind systems. On the other hand, the stacked signal for
regions corresponding to undetected O stars yields log(LX/LBOL) ~ -7.3,
i.e., an emission level comparable to similar Galactic stars despite the lower
metallicity. Other point sources coincide with 11 foreground stars, 6 late-B/A
stars in N11, and many background objects. This observation also uncovers the
extent and detailed spatial properties of the soft, diffuse emission regions,
but the presence of some hotter plasma in their spectra suggests contamination
by the unresolved stellar population.
The Chandra ACIS-I observations of N11 were made in six separate segments
within two months in 2007. As summarized in Table 1, the exposure time of
each segment was 42-49 ks and the roll angle ranged from 130 to 188 degrees
Cleaning of significant background flares, together with a correction for the
dead time of the six observations, resulted in a total of 280 ks useful
exposure for the subsequent analysis. A combination of source detection
algorithms (wavelet, sliding-box, and maximum likelihood centroid fitting)
were applied to unsmoothed data in three bands: soft (S): 0.5-2.0 keV, hard
(H): 2-8 keV, and total (T): 0.5-8 keV. The final source list contains 165
sources with local false detection probability P < 10-6 in at least one
band (Poisson statistics were used in calculating the significance of a
source detection above the local count background). The source detection,
though optimized for point-like sources, includes a few strong peaks of
diffuse X-ray emission, chiefly associated with the SNR N11L, which lies
about ~7' west of the field center.
The authors calculated the net (background-subtracted) count rates in four
sub-bands (S1 = 0.5-1.0 keV, S2 = 1-2 keV, H1 = 2-4 keV and H2 = 4-8 keV,
which were later added to form the count rates in the broader bands (S, H,
and T). Source counts for each sub-band were then extracted within the 70%
energy-encircled radius (EER) of the PSF, whose size depends on the off-axis
angle of the source in the exposure and of the energy band under
consideration. A background correction was also applied. Finally, count rates
were derived by dividing source net counts by their effective exposure times
(values at the source positions in the exposure map of the energy band under
consideration), leading to equivalent on-axis values. It should be noted that
the presented count rates have thus been corrected for the full PSF and for
the effective exposure, which accounts not only for the telescope vignetting,
but also for the degradation of the detector sensitivity over time.
Therefore, the actual number of counts in a detection aperture is not simply
a count rate multiplied by an exposure of 280 ks. The difference could be up
to a factor of ~2, depending on a source's spectral shape.
The authors searched for counterparts to their X-ray sources in several
catalogs: the USNO-B1.0 Catalog (Monet et al. 2003), the Guide Star Catalog
V2.3.2 (GSC, Lasker et al. 2008), the 2MASS All-Sky Catalog of Point Sources
(Cutri et al. 2003), the Magellanic Clouds Photometric Survey (MCPS; Zaritsky
et al. 2004, AJ, 128, 1606), the IRSF Magellanic Clouds Point Source Catalog
(Kato et al. 2007, PASJ, 59, 615)), the DENIS Catalogue toward Magellanic
Clouds (DCMC; Cioni et al. 2000, A&AS, 144, 235), and JHKs photometry of
N11 young stellar objects ([HKN2006]; Hatano et al. 2006, AJ, 132, 2653). A
best correlation radius of 1" was found to be optimal and was thus used to
derive the final list of optical and infrared counterparts to the Chandra
X-ray sources: 71 of the 165 sources have at least one counterpart within 1".
The HEASARC has modified the counterpart names given in this table compared
to those given in the reference paper so that they comply with the forms
recommended by the CDS Dictionary of Nomenclature of Celestial Objects.
M101CXO Catalog
A deep (98.2ks) Chandra Cycle 1 observation has revealed a wealth
of discrete X-ray sources as well as diffuse emission in the nearby face-on
spiral galaxy M 101. From this rich data set, the authors have created a
catalog of the 110 sources from the S3 chip which were detected with a
significance of greater than 3-sigma. This detection threshold
corresponds to a flux of ~ 10^-16 ergs/cm^2/s and a luminosity of
~ 10^36 ergs/s for a distance to M 101 of 7.2 Mpc. The sources display a
distinct correlation with the spiral arms of M101 and include a
variety of X-ray binaries, supersoft sources, supernova remnants, and
other objects of which only ~27 are likely to be background sources.
The 29 brightest sources have enough flux (greater than 100 counts) to perform
at least crude spectral modeling using the HEASARC XSPEC model fitting program.
Most of the sources could be satisfactorily fitted with a simple absorbed
power-law spectrum model; however, eight of the softest sources were better
fitted by an absorbed blackbody model.
M108CXO Catalog
This table contains a list of discrete sources found in a 60-ks Chandra
ACIS-S observation of the isolated edge-on spiral galaxy NGC 3556 (M108). In
the reference paper in which the authors present this table, they also give a
multiwavelength analysis of the various discrete X-ray sources and of the
diffuse X-ray features. Among 33 discrete X-ray sources detected within the
IB = 25 mag arcsec-2 isophotal ellipse of the galaxy, the authors
identify a candidate for the galactic nucleus, an ultraluminous X-ray source
that might be an accreting intermediate-mass black hole, a possible X-ray
binary with a radio counterpart, and two radio-bright giant H II regions.
They also detect large amounts of extraplanar diffuse X-ray emission, which
extend about 10 kpc radially in the disk and >~4 kpc away from the galactic
plane. The diffuse X-ray emission exhibits significant substructures,
possibly representing various blown-out superbubbles or chimneys of hot gas
heated in massive star-forming regions.
This Chandra observation of NGC 3556 (observation ID 2025) was taken between
2001 September 8 and 9 for an exposure of 60 ks. The ACIS-S instrument was at
the focal plane of the telescope.
M16CXO Catalog
Mechanisms regulating the origin of X-rays in young stellar objects and the
correlation with their evolutionary stage are under debate. Studies of the
X-ray properties in young clusters allow us to understand these mechanisms.
One ideal target for this analysis is the Eagle Nebula (M 16), with its
central cluster NGC 6611. At 1750 pc from the Sun, it harbors 93 OB stars,
together with a population of low-mass stars from embedded protostars to
disk-less Class III objects, with age <= 3 Myr. The authors study an archival
78 ks Chandra/ACIS-I observation of NGC 6611 and two new 80-ks observations
of the outer region of M 16, one centered on the Column V and the other on a
region of the molecular cloud with ongoing star formation. They detect 1755
point sources with 1183 candidate cluster members (219 disk-bearing and 964
disk-less), studying the global X-ray properties of M 16 and comparing them
with those of the Orion Nebula Cluster. The authors also compare the level of
X-ray emission of Class II and Class III stars and analyze the X-ray spectral
properties of OB stars. Their study supports the lower level of X-ray
activity for the disk-bearing stars with respect to the disk-less members.
The X-ray luminosity function (XLF) of M 16 is similar to that of Orion,
supporting the universality of the XLF in young clusters. Eighty-five percent
of the O-type stars of NGC 6611 have been detected in X-rays. With only one
possible exception, they show soft spectra with no hard components,
indicating that mechanisms for the production of hard X-ray emission in O
stars are not operating in NGC 6611.
The determination of the absorption corrected X-ray luminosity (LX), as
well as the plasma temperature (kT) and hydrogen column density (NH),
requires the analysis of the X-ray spectra. The authors fit the observed
spectra with thermal plasma (with both one and two temperatures) and
power-law models. They use the APEC ionization-equilibrium thermal plasma
code, assuming the sub-solar elemental abundances of Maggio et al. (2007,
APJ, 660, 1462). The absorption was treated using the WABS model. The
one-temperature (1T) thermal model was applied to all the sources with more
than 25 counts, while the two-temperature (2T) thermal model was applied to
each source with more than 80 counts. The power-law model has been applied to
those sources with hard spectra for which the best-fit thermal model predicts
a plasma temperature kT > 5 keV. When more than one model has been used for a
given source, the authors chose the best model by the chi-squared probability
and visual inspection of the spectrum.
This table contains a description of the X-ray properties of 1754 sources
(one less than stated in the abstract of the reference paper) derived from
three Chandra/ACIS-I observations, together with a source classification
based on the optical and infrared properties of each source. Data come from
three ACIS-I observations (central or 'c', east or 'e', and north-east or
'ne') and many values are not averaged but presented for each observation as
indicated by the parameter prefixes 'c_', 'e_', and 'ne_', respectively.
Source detection has been performed with PWDetect, adopting a threshold
corresponding to 10 spurious detections.
The HEASARC eliminated the 3 parameters describing the plasma temperature of
the second spectral component and its associated negative and positive errors
for sources in the north-east observation, as these were blank for all
entries in the original table as obtained from the CDS.
M17CXO Catalog
This table contains some of the results from a Chandra ACIS observation of
the stellar populations in and around the M17 H II region. The field reveals
886 sources (listed in the present table) with observed X-ray luminosities
(uncorrected for absorption) between ~ 29.3 erg s-1 < log LX < 32.8 erg
s-1, 771 of which have stellar counterparts in infrared images. Spectral
analysis results for the 598 brightest X-ray sources which have photometric
significance of 2.0 or greater) are also given herein. For 546 of the X-ray
sources, the fits used the "wabs(apec)" thermal plasma model in XSPEC
assuming scaled 0.3 times solar photospheric abundances, while for the other
52 X-ray sources for which either the thermal model poorly described the data
or required nonphysical parameters and the X-ray source was not identified
with a known stellar counterpart, the fits used the "wabs(powerlaw)" model in
XSPEC.
In addition to the comprehensive tabulation of X-ray source properties,
several other results were presented in the reference paper:
1. The X-ray luminosity function is calibrated to that of the Orion Nebula
Cluster population to infer a total population of roughly 8000-10,000 stars
in M17, one-third lying in the central NGC 6618 cluster.
2. About 40% of the ACIS sources are heavily obscured with AV > 10 mag. Some
are concentrated around well-studied star-forming regions -- IRS 5/UC1, the
Kleinmann-Wright Object, and M17-North -- but most are distributed across the
field. As previously shown, star formation appears to be widely distributed
in the molecular clouds. X-ray emission is detected from 64 of the hundreds
of Class I protostar candidates that can be identified by near- and
mid-infrared colors. These constitute the most likely protostar candidates
known in M17.
3. The spatial distribution of X-ray stars is complex: in addition to the
central NGC 6618 cluster and well-known embedded groups, we find a new
embedded cluster (designated M17-X), a 2 pc long arc of young stars along
the southwest edge of the M17 H II region, and 0.1 pc substructure within
various populations. These structures may indicate that the populations
are dynamically young.
4. All (14/14) of the known O stars but only about half (19/34) of the known
B0-B3 stars in the M17 field are detected. These stars exhibit the
long-reported correlation between X-ray and bolometric luminosities of LX ~
10-7 Lbol. While many O and early-B stars show the soft X-ray emission
expected from microshocks in their winds or moderately hard emission that
could be caused by magnetically channeled wind shocks, six of these stars
exhibit very hard thermal plasma components (kT > 4 keV) that may be due to
colliding wind binaries. More than 100 candidate new OB stars are found,
including 28 X-ray detected intermediate- and high-mass protostar candidates
with infrared excesses.
5. Only a small fraction (perhaps 10%) of X-ray selected high- and
intermediate-mass stars exhibit K-band-emitting protoplanetary disks,
providing further evidence that inner disks evolve very rapidly around
more massive stars.
M31CFCXO Catalog
The central field of the Andromeda galaxy (M 31) was monitored from 2006 to
2012 using the Chandra HRC-I detector (about 0.1 - 10 keV energy range) with
the main aim of detecting X-rays from optical novae. The authors present a
systematic analysis of all X-ray sources found in the 41 nova monitoring
observations, along with 23 M 31 central field HRC-I observations available
from the Chandra data archive starting in December 1999. Based on these
observations, they studied the X-ray long-term variability of the source
population and especially of the X-ray binaries in M31. The authors created a
catalog of sources detected in the 64 available observations that adds up to
a total exposure time of about 1 Ms. To study the variability, they developed
a processing pipeline to derive long-term Chandra HRC-I light curves for each
source over the 13 years of observations, and also searched for extended
X-ray sources in the merged images. This table contains the point-source
catalog of 318 X-ray sources with detailed long-term variability information,
28 of which are published for the first time. The spatial and temporal
resolution of the catalog allows the authors to classify 115 X-ray binary
candidates showing high X-ray variability or even outbursts, as well as 14
globular cluster X-ray binary candidates showing no significant variability.
The analysis may suggest that outburst sources are less frequent in globular
clusters than in the field of M 31. Seven supernova remnants (not included in
the point-source catalog) were detected, one of which is a new candidate, and
also the first X-rays from a known radio supernova remnant were resolved. In
addition to 33 known optical nova/X-ray source correlations, the authors
discovered one previously unknown super-soft X-ray outburst and several new
nova candidates. A large sample of detailed long-term X-ray light curves of
sources in the M31 central field has been obtained in this study (see
Appendix B.1 of the reference paper), which helps in understanding the X-ray
population of our neighboring spiral galaxy M 31.
Based on all the available Chandra HRC-I observations (see Table A.1 in the
reference paper for the complete list), a source catalog has
been created (available in this HEASARC table) and the energy flux of each
source in every individual observation derived (these are not available in
this HEASARC table, but are obtainable at the CDS: for more details, see the
files ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/555/A65/ReadMe
and ftp://cdsarc.u-strasbg.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz). One
thing to be aware of is that, in the latter file, upper limits are denoted
by a '>' symbol rather than the more usual '<' symbol!).
These fluxes were calculated assuming a generic power law spectrum and Galactic
foreground absorption for each source.
M31CXO2 Catalog
The authors explore the population of X-ray point sources in the bulge of M
31 so as to contrast properties of various subpopulations, such as persistent
and transient sources and primordial LMXBs and dynamically formed ones. Based
on the data from 26 archival Chandra ACIS observations with aim-points within
10 arcminutes of the center of M 31 (J2000 coordinates of 00:42:44.31,
+41:16:09.4), the authors study the source content and properties of various
subpopulations of X-ray sources to a maximum distance of 12 arcminutes from
the center of M 31.
To a limiting luminosity of ~1035 erg s-1, the authors find 263 X-ray
point sources, with ~1/3 of these being background galaxies. A study of the
spatial distribution and the luminosity function of the X-ray sources shows
that the distribution of primordial LMXBs is consistent with the distribution
of the K-band light and that their luminosity function flattens below ~1037
erg s-1 to the dN/dL ~ L-1 law in agreement with the behavior found
earlier for LMXBs in the Milky Way and in Cen A. Within a radius of 12
arcminutes, the luminosity function is independent of distance to the center
of M 31, in contrast to earlier Chandra studies. The LMXBs located in
globular clusters and within ~1 arcminute from the center of M 31 are
presumably created via dynamical interactions. The dynamical origin of the r
< 1 arcminute sources is strongly suggested by their radial distribution
which follows the rho*2 profile rather than the K-band light distribution.
Their luminosity function shows a prominent fall-off below log(LX) <~ 36.5.
Although the statistics are insufficient to claim a genuine low-luminosity
cut-off in the luminosity function, the best fit power-law with a slope of
-0.6 +/- 0.2 is significantly flatter than the dN/dL ~ L-1 law. The authors
also searched for transients and found 28 sources that varied by a factor
larger than 20. Their spatial distribution follows the distribution of the
persistent LMXBs within the accuracy allowed by the limited number of
transients.
M31CXOHRC2 Catalog
The authors have obtained 17 epochs of Chandra High Resolution Camera (HRC)
snapshot images, each covering most of the M31 disk. The data cover a total
baseline of ~2.5 yr and contain a mean effective exposure of 17 ks. The
authors measured the mean fluxes and long-term light curves for 166 objects
detected in these data. At least 25% of the sources show significant
variability. The cumulative luminosity function (CLF) of the disk sources is
well fitted by a power law with a slope comparable to those observed in
typical elliptical galaxies. The CLF of the bulge is a broken power law
similar to measurements made by previous surveys. The authors note several
sources in the southwestern disk with LX > 1037 ergs s-1. They
cross-correlate all of their sources with published optical and radio
catalogs, as well as new optical data, finding counterpart candidates for 55
sources. In addition, 17 sources are likely X-ray transients. Finally, the
frequency of bright X-ray transients in the M31 bulge suggests that the ratio
of neutron star to black hole primaries in low-mass X-ray binaries (NS/BH) is
1.
The data for this project were originally part of a survey program to look
for X-ray transients in M31. Nearly every month from 1999 November to 2001
February, Chandra took HRC-I images of five fields covering most of M31.
Observations were then made every few months until 2002 June. The details of
the 81 Chandra observations are summarized in Table 1 of the reference paper,
which is available in a machine-readable form at
http://cdsarc.u-strasbg.fr/ftp/cats/J_ApJ/609/735/. The authors combined all
the data into three data sets using the task merge_all. One set contained the
data for the northern half of the galaxy, another contained the southern
half, and the last contained the center. The authors searched for sources in
the three data sets using the CIAO task wavdetect. They ran this task
searching for sources on four size scales: 1, 2, 4, and 8 pixels. The pixels
in the merged images were 1 arcsecond in the central 18 arcmin by 18 arcmin
and 2 arcsec outside of this region. By searching on several scales,
wavdetect is able to overcome the large changes in the size of the Chandra
PSF from about 0.5 arcsec near the center of the field to over 10 arcsec in
the outer regions of the field. A total of 166 sources were detected above
their 3.5-sigma detection threshold.
M31CXOXRAY Catalog
This table countains the M 31 Central Region Catalog of
Chandra X-Ray Point Sources. It is based on Chandra observations of the
central region of M 31. By combining eight Chandra ACIS-I observations which
were taken between 1999 and 2001, the authors have identified 204 X-ray
sources within the central ~17'x17' region of M 31, with a detection limit
of ~2x1035 erg/s. Of these 204 X-ray sources, 22 are identified with
globular clusters, two with supernova remnants, nine with planetary nebulae,
and nine with supersoft sources. By comparing individual images, about 50%
of the sources were found to be variable on timescales of months.
The authors also found 13 transients, with light curves showing a variety
of shapes. They also extracted the energy spectra of the 20 brightest
sources; they can be well fitted by a single power law with a mean photon
index of 1.8. The spectral shapes of 12 sources were variable, suggesting
that they went through state changes.
All sources in the catalog have S/N > 2.5 and only five have S/N < 3.0.
The detection limit for the sources varies across the image due to the
variation of exposure time, background, and instrumental PSF, and is
highest near the edges, where the PSF broadens rapidly and the exposure
time is lowest. Over the inner 4' of the field, the detection limit is
2.1 x 10-4 ct/s, which is equivalent to an X-ray luminosity of about
2 x 1035 erg/s.
Additional information about optical identifications and cross-correlated
ROSAT X-ray sources not provided in this HEASARC table is available in the
published paper (Tables 4 and 5) and/or the CDS at
ftp://cdsarc.u-strasbg.fr/pub/cats/J/ApJ/577/738/ (table4.dat & table5.dat).
M31PHATCXO Catalog
The X-ray source populations within galaxies are typically difficult to
identify and classify with X-ray data alone. The authors break through this
barrier by combining deep new Chandra ACIS-I observations with extensive
Hubble Space Telescope (HST) imaging from the Panchromatic Hubble Andromeda
Treasury (PHAT) of the M 31 disk. They detect 373 X-ray sources down to
0.35-8.0keV flux of 10-15erg/cm-2/s over 0.4deg2, 170 of which are
reported for the first time. The authors identify optical counterpart
candidates for 188 of the 373 sources, after using the HST data to correct
the absolute astrometry of our Chandra imaging to 0.1". While 58 of these 188
are associated with point sources potentially in M 31, over half (107) of the
counterpart candidates are extended background galaxies, 5 are star clusters,
12 are foreground stars, and 6 are supernova remnants. Sources with no clear
counterpart candidate are most likely to be undetected background galaxies
and low-mass X-ray binaries in M 31. The hardest sources in the 1-8keV band
tend to be matched to background galaxies. The 58 point sources that are not
consistent with foreground stars are bright enough that they could be
high-mass stars in M 31; however, all but 8 have optical colors inconsistent
with single stars, suggesting that many could be background galaxies or
binary counterparts.
For point-like counterparts, the authors examine the star formation history
of the surrounding stellar populations to look for a young component that
could be associated with a high-mass X-ray binary. The associated star
formation histories for sources in the catalog are available in the linked
table M31PHATSFH.
In 2015 October, the authors observed the Panchromatic Hubble Andromeda
Treasury (PHAT) footprint with Chandra with 7 pointings. The footprints are
overlaid on a GALEX NUV image of M 31, along with the corresponding HST
coverage, in Figure 1 of the reference paper. At each pointing they observed
for about 50ks in VF mode (Chandra ObsID 17008 to 17014 spanning 2015 Oct 06
to 2015 Oct 26).
M31PHATSFH Catalog
The X-ray source populations within galaxies are typically difficult to
identify and classify with X-ray data alone. The authors break through this
barrier by combining deep new Chandra ACIS-I observations with extensive
Hubble Space Telescope (HST) imaging from the Panchromatic Hubble Andromeda
Treasury (PHAT) of the M 31 disk. They detect 373 X-ray sources down to
0.35-8.0keV flux of 10-15erg/cm-2/s over 0.4deg2, 170 of which are
reported for the first time. The authors identify optical counterpart
candidates for 188 of the 373 sources, after using the HST data to correct
the absolute astrometry of our Chandra imaging to 0.1". These data are
available at M31PHATCXO.
For point-like counterparts, the authors examine the star formation history
of the surrounding stellar populations to look for a young component that
could be associated with a high-mass X-ray binary. This table presents the
star formation histories for a subset of sources in the
M31PHATCXO catalog.
About one-third of the point sources are not physically associated
with a young population, and are therefore more likely to be
background galaxies. For the 40 point-like counterpart candidates
associated with young populations, the authors find that their age
distribution has two peaks at 15-20Myr and 40-50Myr. Considering
only the 8 counterpart candidates with typical high-mass main-sequence
optical star colors, their age distribution peaks mimic those of the
sample of 40. Finally, the authors find that intrinsic faintness, and
not extinction, is the main limitation for finding further counterpart candidates.
In 2015 October, the authors observed the Panchromatic Hubble Andromeda
Treasury (PHAT) footprint with Chandra with 7 pointings. The footprints are
overlaid on a GALEX NUV image of M 31, along with the corresponding HST
coverage, in Figure 1 of the reference paper. At each pointing they observed
for about 50 ks in VF mode (Chandra ObsID 17008 to 17014 spanning 2015 Oct 06
to 2015 Oct 26).
M33CHASE Catalog
This table contains the final source catalog of the Chandra ACIS
Survey of M33 (ChASeM33). With a total exposure time of 1.4 Ms, ChASeM33 covers
~70% of the D25 isophote (radial extent ~ 4.0 kpc) of M33 and provides the
deepest, most complete, and detailed look at a spiral galaxy in X-rays. The
source catalog includes 662 sources, reaches a limiting unabsorbed luminosity
of ~2.4 x 1034 erg s-1 in the 0.35-8.0 keV energy band, and contains source
positions, source net counts, fluxes and significances in several energy bands,
and information on source variability. The analysis challenges posed by
ChASeM33 and the techniques adopted to address these challenges are discussed.
To constrain the nature of the detected X-ray source, hardness ratios were
constructed and spectra were fit for 254 sources, follow-up Multiple Mirror
Telescope (MMT) spectra of 116 sources were acquired, and cross-correlations
with previous X-ray catalogs and other multi-wavelength data were generated.
Based on this effort, 183 of the 662 ChASeM33 sources could be identified.
Finally, in the reference paper, the luminosity function (LF) for the detected
point sources as well as the one for the X-ray binaries (XRBs) in M33 were
presented. The LFs in the soft band (0.5-2.0 keV) and the hard band (2.0-8.0
keV) have a limiting luminosity at the 90% completeness limit of 4.0 x 1034
erg s-1 and 1.6 x 1035 erg s-1 (for an assumed distance D to M33 of 817
kpc), respectively, which is significantly lower than what was reported by
previous XRB population studies in galaxies more distant than M33. The
resulting distribution is consistent with a dominant population of high-mass
XRBs as would be expected for M33.
The list of all the Chandra ACIS observations that were used in the
construction of this source catalog is given in table 2 of the 2011
reference paper.
X-ray source properties, such as counts, dns values, and photon
fluxes were computed in the following energy bands:
Band Energy Range (keV)
1 0.5 - 8.0
2 0.5 - 2.0
3 2.0 - 8.0
4 0.35- 8.0
5 0.35- 1.1
6 1.1 - 2.6
7 2.6 - 8.0
8 0.35- 2.0
M33CXOXRAY Catalog
This database table contains a source list for three Chandra observations
of the Local Group galaxy M 33. The observations were centered on the nucleus
and on the star-forming region NGC 604. A total of 261 sources were detected
in an area of about 0.2 square degrees down to a flux limit of 3 x 10-16
erg/s/cm2, which corresponds to a luminosity of ~2 x 1034 erg/s at a
distance of 840 kpc. The luminosity functions of the X-ray sources observed
in M 33 have been constructed and are consistent with those of other
star-forming galaxies, taking into account background contamination.
In addition, the combination of X-ray color analysis and the existence of
"blue" optical counterparts strongly indicates that the X-ray point source
population in M 33 consists of young objects. Above 3 x 1035 erg/s, there
are few X-ray sources in the locus of the X-ray hardness ratio diagram that
is generally populated by low-mass X-ray binaries.
Notice that each of the 261 X-ray sources in the source list has 3 entries
in this table, one for each separate Chandra observation, making a total
of 783 entries.
The Chandra datasets from which this source list was compiled are available
by querying CHANMASTER for obsids 786, 1730, and 2023.
M37CXO Catalog
Empirical calibrations of the stellar age-rotation-activity relation (ARAR)
rely on observations of the co-eval populations of stars in open clusters.
The authors used the Chandra X-ray Observatory to study M 37 (NGC 2099), a
500-Myr-old open cluster that has been extensively surveyed for rotation
periods (Prot). M 37 was observed almost continuously for five days, for a
total of 440.5 ks, to measure stellar X-ray luminosities (LX), a proxy for
coronal activity, across a wide range of masses. The cluster's membership
catalog was revisited to calculate updated membership probabilities from
photometric data and each star's distance to the cluster center. The result
is a comprehensive sample of 1699 M 37 members: 426 with Prot, 278 with
X-ray detections, and 76 with both. The authors calculate Rossby numbers,
Ro= Prot/tau , where tau is the convective turnover time, and ratios of
the X-ray-to-bolometric luminosity, LX/Lbol, to minimize mass
dependencies in their characterization of the rotation-coronal activity
relation at 500 Myr. They find that fast rotators, for which Ro < 0.09 +/-
0.01, show saturated levels of activity, with log(LX/Lbol) = -3.06 +/-
0.04. For Ro >= 0.09 +/- 0.01, activity is unsaturated and follows a power
law of the form Rbetao , where beta = -2.03 (-0.14, +0.17). This is the
largest sample available for analyzing the dependence of coronal emission on
rotation for a single-aged population, covering stellar masses in the range
0.4 - 1.3 solar masses, Prot in the range 0.4 - 12.8 days, and LX in the
range 1028.4 - 1030.5 erg s-1. These results make M 37 a new benchmark
open cluster for calibrating the ARAR at ages of ~ 500 Myr.
The central field of M 37 was observed five separate times between 2011
November 14 20:58 and 2011 November 1915:31 UTC for a total of 440.5 ks with
the Advanced CCD Imaging Spectrometer (ACIS). The four ACIS-I chips and the
ACIS-S3 chip were used in Very Faint telemetry mode to improve the screening
of background events and thus increase the sensitivity of ACIS to faint
sources. The exposure-weighted average aimpoint of the 16.9 x 16.9 arcmin2
ACIS-I field of view is RA = 05h 52m 17.86s,Dec = +32o 33' 48.23"
(J2000). The pitch angle for four observations was 103 degrees; due to
scheduling constraints, it was 253 degrees for the fifth. Table 1 in the
reference paper provides the basic information for the 5 Chandra observations
and Figure 1 in that paper shows their footprints superimposed on a 40' x 40'
i' image centered on M 37 obtained by Hartman et al. (2008, ApJ, 675, 1233,
hereafter HA08) with the Megacam on the MMT telescope.
This HEASARC table contains all of the data from Table 3 of the reference
paper, the M 37 Chandra catalog of 774 X-ray sources, and the data from Table
5, the catalog of optical objects, for those objects which have been
identified as optical counterparts to the X-ray sources. It does not contain
entries for those optical objects in Table 5 which lack X-ray counterparts.
M51CXO Catalog
This table contains the results of two Chandra observations
(separated by 1 year) of the population of X-ray sources in the spiral galaxy
M 51 (NGC 5194 and NGC 5195). One hundred and thirteen X-ray sources have been
detected in an 8.4' x 8.4'(20.4 x 20.4kpc) region, and 84 and 12 of them
project within the disks of NGC 5194 and NGC 5195, respectively. Nine
and 28 sources have luminosities exceeding 1 x 10^39 erg/s (ultraluminous
X-ray sources or ULXs) and 1 x 10^38 erg/s in the 0.5 - 8 keV band,
respectively, assuming that they are associated with M 51. The number of ULXs
is much higher than found in most normal spiral and elliptical galaxies. Most
of the X-ray sources and all seven of the ULXs in NGC 5194 are located in, or
close to, a spiral arm, suggesting a connection with recent star formation.
The Chandra observations of M 51 were performed on 2000 June 20 and 2001
June 23 with the ACIS instrument. The background was stable in both
observations, and effective exposure times of 14.9 and 26.8ks were
obtained for the observations in 2000 and 2001, respectively.
M51CXO2 Catalog
The authors obtained a deep X-ray image of the nearby galaxy M 51 using the
Chandra X-Ray Observatory. Here the catalog of X-ray sources detected in
point-source population is provided in the reference paper. The authors find
298 sources within the D25 radii (the apparent major isophotal galactic
radii measured at or reduced to the surface brightness level muB = 25.0
B-mag per square arcsecond) of NGC 5194 and NGC 5195, of which 20% are
variable, a dozen are classical transients, and another half dozen are
transient-like sources. The typical number of active ultraluminous X-ray
sources in any given observation is ~5, and only two of those sources persist
in an ultraluminous state over the 12 years of observations. Given reasonable
assumptions about the supernova remnant population, the luminosity function
is well described by a power law with an index between 1.55 and 1.7, only
slightly shallower than that found for populations dominated by high-mass
X-ray binaries (HMXBs), which suggests that the binary population in NGC 5194
is also dominated by HMXBs. The luminosity function of NGC 5195 is more
consistent with a low-mass X-ray binary dominated population.
This deep study of M51 is composed of 107 ks of archival Chandra
observations, to which the authors added another 745 ks of observations. The
Chandra ObsIDs and parameters of all of the observations used in this study
(which span from June 2000 to October 2012) are given in Table 2 of the
reference paper. All of the observations were made with the ACIS-S array. The
authors used the ACIS Extract software package (AE) to perform the
photometry. For each source, AE extracted a source region whose size and
shape were based on the local PSF, and a background region whose size and
shape were based on the size of the local PSF and the location of nearby
sources. Source properties were then calculated in a standard manner. Of
particular importance in this analysis is the prob_no_source parameter, which
is the probability that one could measure the observed count rate in the
absence of a source. The authors took a source to be significant only if this
parameter was < 5 x 10-6. At this probability threshold, one would expect a
single spurious source per field, or roughly 1.5 spurious sources within the
D25 regions. As they used the same value in their analysis of M83 (Long et
al. 2014, ApJS, 212, 21, the source catalog from which is available in the
HEASARC database as the M83CXO table), the
two catalogs are directly comparable.
M67CXO Catalog
The M 67 Chandra X-Ray Point Source Catalog contains the results
of a 47 ks Chandra/ACIS observation of the old (4 Gyr) open cluster M67.
The authors detected 25 proper-motion cluster members (including ten new
sources) and 12 sources (all new) that they suspect to be M 67 members from
their locations close to the main sequence (1 < B-V < 1.7). Of the detected
members, 23 are binaries. In addition to cluster members, about 100 background
sources were detected, many of which were identified with faint objects in
the ESO Imaging Survey (EIS, Momany et al. 2001, A&A, 379, 436).
This table summarizes the X-ray properties of the 158 sources which were
detected by Chandra in this observation, and also lists the ROSAT (Belloni
et al., 1998A&A...335..517B) and optical (candidate) counterparts.
M71CXO Catalog
The authors observed the nearby, low-density globular cluster M71 (NGC 6838)
with the Chandra X-Ray Observatory to study its faint X-ray populations. Five
X-ray sources were found inside the cluster core radius, including the known
eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light
curve of the source coincident with this MSP shows marginal evidence for
periodicity at the binary period of 4.2hr. Its hard X-ray spectrum and
luminosity resemble those of other eclipsing binary MSPs in 47 Tuc,
suggesting a similar shock origin of the X-ray emission. A further 24 X-ray
sources were found within the half-mass radius rh, reaching to a limiting
luminosity of 1.5 x 1030 ergs/s (0.3-8 keV). From a radial distribution
analysis, the authors find that 18 +/- 6 of these 29 sources are associated
with M71, somewhat more than predicted, and that 11 +/- 6 are background
sources, both Galactic and extragalactic. M71 appears to have more X-ray
sources in the range LX = 1030 - 1031 ergs/s than expected by
extrapolating from other studied clusters using either mass or collision
frequency. In their paper, the authors explore the spectra and variability of
these sources and describe the results of ground-based optical counterpart
searches.
The authors obtained a 52.4 ks Chandra observation (ObsID 5434) of M71
(nominal center of cluster at J2000.0 RA and Dec of 19 53 46.1 +18 46 42) on
2004 December 20-21 using the Advanced CCD Imaging Spectrometer (ACIS) in
very faint (VF), timed-exposure mode with a 3.141s frame time. They searched
for X-ray sources in the observed field by employing techniques described in
Tennant (2006, AJ, 132, 1372) which use a circular Gaussian approximation to
the point-spread function (PSF). Within twice the M71 half-mass radius (rh
= 1.65 arcminutes), they set the signal-to-noise threshold (S/N) for
detection to 2.0, but also required the number of source counts to be at
least 5 times the statistical uncertainty in the local background estimate.
The empirical relation derived by Tennant, Cmin = (S/N)2/0.81, then
implies a point-source sensitivity limit of about 4.9 counts for rM71 <=
2rh and in the energy band 0.3-8.0 keV. Because of the increase in PSF size
with off-axis distance and the associated increase in background within a
detection cell, for RM71 > 2rh they set the S/N threshold for detection
to 2.4 and again required the number of source counts to be at least 5 times
the statistical uncertainty in the local background estimate. The
point-source sensitivity limit thus rises to about seven counts.
This table contains 63 X-ray sources and their optical/infrared counterpart
information, if any, for those sources with rM71 <= 2r_h which are listed
in Table 1 of the reference paper: these sources have name prefixes of s01 to
s63. It also contains 73 X-ray sources and their optical/infrared counterpart
information, if any, for those sources with rM71 > 2r_h which are listed in
Table 2 of the reference paper: these sources have name prefixes of ss01 to
ss59 and is01 to is14. Each entry in this table corresponds to an X-ray
source if there is no counterpart information or only a single identified
counterpart or to a particular X-ray source and counterpart match if there
are multiple counterpart identifications. There are thus 165 entries in this
HEASARC table corresponding to 136 X-ray sources.
M81CXO Catalog
A Chandra X-Ray Observatory ACIS-S imaging observation is used to study the
population of X-ray sources in the nearby (3.6 Mpc) Sab galaxy M 81 (NGC
3031). A total of 177 sources are detected, with 124 located within the D_25
isophote to a limiting X-ray luminosity of ~ 3 x 1036 erg/s. Source
positions, count rates, luminosities in the 0.3 - 8.0 keV band, limiting
optical magnitudes, and potential counterpart identifications are tabulated.
Spectral and timing analysis of the 36 brightest sources are reported,
including the low-luminosity active galactic nucleus, SN 1993J, and the
Einstein-discovered ultraluminous X-ray source X6.
The primary X-ray data set is a 49926 s observation of M81 obtained on 2000
May 7 with the Chandra Advanced CCD Imaging Spectrometer (ACIS) spectroscopy
array operating in imaging mode. The X-ray data were reprocessed by the
Chandra X-ray Center (CXC) on 2001 January 4. These reprocessed data were
used in this work. There are no significant differences between the
reprocessed data and the originally distributed data analyzed by Tennant et
al. (2001ApJ...549L..43T). The observation was taken in faint timed exposure
mode at 3.241 s/frame at a focal plane temperature of -120 C. Standard CXC
processing has applied aspect corrections and compensated for spacecraft
dither.
The primary target, SN 1993J, was located near the nominal aimpoint on the
back-illuminated (BI) device S3. The nucleus of M81 lies 2.79' from SN 1993J
toward the center of S3 in this observation. Accurate positions of these two
objects and two G0 stars located on device S2 were used to identify any
offset and to determine absolute locations of the remaining Chandra sources
as well as objects in other X-ray images and those obtained at other
wavelengths. No offset correction was applied to the Chandra X-ray positions.
M81CXO2 Catalog
This table contains the source table from an analysis of 15 Chandra ACIS
observations of the nearby spiral galaxy M81 taken over the course of six
weeks in 2005 May-July. Each observation reaches a sensitivity of ~1037 erg
s-1. With these observations and one previous deeper Chandra observation
(the properties of which are described in Table 1 and Section 2 of the
reference paper), the authors have compiled a master source list of 265 point
sources, extracted and fitted their spectra, and differentiated basic
populations of sources through their colors. They also carried out
variability analyses of individual point sources and of X-ray luminosity
functions (XLFs) in multiple regions of M 81 on timescales of days, months,
and years. They find that, despite measuring significant variability in a
considerable fraction of sources, snapshot observations provide a consistent
determination of the XLF of M81. They also fit the XLFs for multiple regions
of M81 and, using common parametrization, compare these luminosity
functions to those of two other spiral galaxies, M31 and the Milky Way.
This table contains the 265 point sources at or above the 99.9% probability
level of being real according to AE's PROB_NO_SOURCE statistic (the "master"
source list), and 11 additional "borderline" sources which have 99.0-99.9%
probability of being real according to AE's PROB_NO_SOURCE statistic, for a
total of 276 sources whose properties were described in Tables 3 and 4 of the
reference paper. The 265 "master" sources have source numbers from 1 to 265
while the 11 "borderline" sources have source numbers beginning with 'B',
e.g., they have source numbers 'B1' to 'B11'. Note that only coordinates are
listed for 3 sources in the master source list (source numbers 234, 241 and
262) and 2 sources in the borderline source list (B8 and B9) because they
were only in the field of view (on chip) of one observation (ObsID 735). Six
additional sources near the center of M81 which were found using maximum
likelihood image reconstruction are not included in either the master or
borderline source lists contained herein but their positions are listed in
table 2 of the reference paper.
M83CXO Catalog
The authors of this table have obtained a series of deep X-ray images of the
nearby (4.61 Mpc) galaxy M 83 using Chandra, with a total exposure of 729 ks.
Combining the new data with earlier archival observations totaling 61 ks,
they find 378 point sources within the D25 contour of the galaxy. The
authors find 80 more sources, mostly background active galactic nuclei
(AGNs), outside of the D25 contour. Of the X-ray sources, 47 have been
detected in a new radio survey of M 83 obtained using the Australia Telescope
Compact Array (ATCA). Of the X-ray sources, at least 87 seem likely to be
supernova remnants (SNRs), based on a combination of their properties in
X-rays and at other wavelengths. The authors attempt to classify the point
source population of M 83 through a combination of spectral and temporal
analysis. As part of this effort, in the reference paper they carry out an
initial spectral analysis of the 29 brightest X-ray sources. The soft X-ray
sources in the disk, many of which are SNRs, are associated with the spiral
arms, while the harder X-ray sources, mostly X-ray binaries (XRBs), do not
appear to be. After eliminating AGNs, foreground stars, and identified SNRs
from the sample, the authors construct the cumulative luminosity function
(CLF) of XRBs brighter than 8 x 1035 erg s-1. Despite M 83's relatively
high star formation rate, the CLF indicates that most of the XRBs in the disk
are low mass X-ray binaries (XRBs).
The X-ray observations of M 83 in this survey were all carried out with the
ACIS-S in order to maximize the sensitivity to soft X-ray sources, such as
SNRs, and to diffuse emission. The nucleus of M 83 was centered in the field
of the back-illuminated S3 chip to provide reasonably uniform coverage of M
83. In addition to the S3 chip, data were also obtained from chips S1, S2,
S4, I2, and I3. All of the observations were made in the "very faint" mode to
optimize background subtraction. Observations were spaced over a period of
one year from 2010 December to 2011 December, as indicated in Table 1 of the
reference paper. The only difference among observations was the roll
orientation of the spacecraft and the differing exposure times. All of the
observations were nominal, and yielded a total of 729 ks of useful data. In
order to maximize their sensitivity and more importantly to improve their
ability to identify time variable sources, the authors included in their
analysis earlier Chandra observations of M 83 in 2000 and 2001 totaling 61 ks
which were obtained by G. Rieke (Prop ID. 1600489) and by A. Prestwich (Prop
ID. 267005758). These data were obtained in a very similar manner to that of
the present survey, and increased the total exposure to 790 ks.
The authors used ACIS EXTRACT (AE) to derive net count rates from the sources
in various energy bands: 0.35 - 8.0 keV (total or T), 0.35 - 1.1 keV (soft or
S), 1.1 - 2.6 keV (medium or M), 2.6 - 8.0 keV (hard or H), 0.5 - 2.0 keV
("normal" soft band) and 2.0 - 8.0 keV ("normal" hard band). Their choice of
these bands was based on a variety of overlapping goals. The broad 0.35 - 8.0
keV band samples the full energy range accessible to Chandra observations. The
three bands S, M and H provide energy ranges intended to classify sources on
the basis of their hardness ratios. The boundary at 1.1 keV, in particular, is
just above the region containing strong features due to Ne and Fe seen in the
spectra of most SNRs. The 0.5 - 2.0 keV and 2.0 - 8.0 keV bands are
needed because number counts of active galactic nuclei (AGNs) and of X-ray
binary populations are normally carried out in these bands and because the
0.5 - 2.0 keV band, encompassing the peak of the response curve, provides
better statistics for some purposes than S+M. The AE count rates were used to
establish which of the sources in the candidate list were statistically valid.
The authors retained any source that had a probability-of-no-source < 5 x
10-6 in any one of these bands in the total data set. For their final run of
AE, their list of source candidates had 847 potential sources. Of those, they
find a total of 458 valid point sources, whose properties are listed in this
table. Of the 458 point sources, 378 are located within the area defined by
the D25 ellipse of the galaxy (which the authors take to have a major axis
diameter of 12.9 arcminutes), and the remaining 80 are outside this region.
There were 43 sources in the nuclear region (defined to be any source within a
projected radius of 0.5 kpc from the optical nucleus).
M83XRBCXO Catalog
Building on recent work by Chandar+ (2020, J/ApJ/890/150), the authors
constructed X-ray luminosity functions (XLFs) for different classes of X-ray
binary (XRB) donors in the nearby star-forming galaxy M 83. Rather than
classifying low-versus high-mass XRBs based on the scaling of the number of
X-ray sources with stellar mass and star formation rate, respectively, this
catalog utilized multi-band Hubble Space Telescope imaging data to classify
each Chandra-detected compact X-ray source as a low-mass (i.e., donor mass <
~3Msun), high-mass (donor mass > ~8Msun), or intermediate-mass XRB based
on either the location of its candidate counterpart on optical
color-magnitude diagrams or the age of its host star cluster. In addition to
the standard (single and/or truncated) power-law functional shape, the
authors approximated the resulting XLFs with a Schechter function. They
identified a marginally significant (at the 1-sigma to 2-sigma level)
exponential downturn for the high-mass XRB XLF, at l~38.48-0.33+0.52 (in
log CGS units). In contrast, the low- and intermediate-mass XRB XLFs, as well
as the total XLF of M 83, are formally consistent with sampling statistics
from a single power law. This method suggests a non-negligible contribution
from low- and possibly intermediate-mass XRBs to the total XRB XLF of M 83,
i.e., between 20% and 50%, in broad agreement with X-ray-based XLFs. More
generally, the authors caution against considerable contamination from X-ray
emitting supernova remnants to the published, X-ray-based XLFs of M 83, and
possibly all actively star-forming galaxies.
This table presents a fully classified catalog of X-ray sources in M 83 that
builds upon the deep Chandra ACIS imaging data published in Lehmer+ 2019
(J/ApJS/243/3). Out of a total of 456 point-like sources brighter than
1035erg/s, this work restricts the analysis to the 325 objects that fall
within the M 83 HST footprint.
HST observations of M 83 were taken with the WFC3/UVIS instrument, spanning
seven fields that each cover approximately 162" x 162" for a total mosaic
area of ~43 arcmin2. All observations were obtained between 2009 August and
2012 September by R. O'Connell (Prop ID. 11360) and W. Blair (Prop ID.
12513), with exposure times ranging from ~1.2 to 2.7 ks for each image. Images
were downloaded from the Hubble Legacy Archive (HLA). In general, BVI images
are created using the F438W, F547M, and F814W filters. The central field,
which includes the galaxy nucleus, uses the broader F555W V-band filter,
rather than F547M. The authors also use U-band images (F336W) to help
calculate cluster ages.
M87CXO Catalog
The ACIS instrument on board the Chandra X-Ray Observatory has been used to
carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M
87 (NGC 4486), the giant elliptical galaxy near the dynamical center of the
Virgo Cluster. These images - with a total exposure time of 154 ks - are the
deepest X-ray observations obtained as of 2004 of M 87. The authors
identified 174 X-ray point sources, (contained in this Browse table) of which
~ 150 are likely LMXBs. This LMXB catalog was combined with deep F475W and
F850LP images taken with ACS on the Hubble Space Telescope (HST) (as part of
the ACS Virgo Cluster Survey) to examine the connection between LMXBs and
globular clusters in M87. Of the 1688 globular clusters in the authors'
catalog, a fraction fX = 3.6% +/- 0.5% contain an LMXB.
M 87 (NGC 4486) was observed with the Chandra Advanced CCD Imaging
Spectrometer (ACIS) for 121 ks on 2002 July 5-6. In this table, only the S3
chip data are used. The data were processed following the CIAO data reduction
threads, including a correction for charge transfer inefficiency (CTI). In
addition, the authors used 38 ks of archival ACIS observations of M 87 taken
on 2000 July 29. These data were processed in a fashion similar to the 2002
July data, except that no CTI correction was possible because the data were
telemetered in graded mode. All reductions were carried out with CIAO,
version 2.3, coupled with CALDB, version 2.21. In order to combine the event
files into a single image for point-source detection, the authors obtained
relative offsets by matching the celestial coordinates of two X-ray point
sources. The relative offset was ~ 0.5". The total exposure time of the
co-added image, excluding four background flares totaling ~ 2.5 ks, was 154 ks.
MONR2CXO Catalog
The Monoceros R2 (Mon R2) Cloud X-Ray Point Source Catalog
contains the results of the Chandra ACIS-I observation of the central
region of this high-mass star-forming region (SFR), which lies at a
distance of 830pc. With a deep exposure of ~ 100 ks, the authors detected
368 X-ray sources, ~80% of which were identified with near-infrared (NIR)
counterparts. They systematically analyzed the spectra and time variability
of most of the X-ray emitting sources and provide a comprehensive X-ray
source catalog for the first time. Using the J-, H- and K-bands magnitudes
of the NIR counterparts, they have estimated the evolutionary phase,
classical T Tauri (CTT) stars and weak-lined T Tauri (WTT) stars, and the
masses of the X-ray emitting sources, and have analyzed their X-ray
properties as a function of age and mass. They found a marginal hint that
CTT stars have a slightly higher temperature (2.4 keV) that of WTT stars
(2.0 keV). A significant fraction of the high- and intermediate-mass
sources have time variability and high plasma temperatures (2.7 keV)
simailar to those of the low-mass stars (2.0 keV). This supports earlier
proposals that high- and intermediate-mass young stellar objects emit
X-rays via magnetic activity. The authors also found a significant
difference in the spatial distribution between X-ray and NIR sources.
MOXC Catalog
This table contains the Massive Star-forming Regions (MSFRs) Omnibus X-ray
Catalog (MOXC), a compendium of X-ray point sources from Chandra/ACIS
observations of a selection of MSFRs across the Galaxy, plus 30 Doradus in
the Large Magellanic Cloud. MOXC consists of 20,623 X-ray point sources from
12 MSFRs with distances ranging from 1.7 kpc to 50 kpc, and comprises Table 3
of the reference paper. In their paper, the authors show the morphology of
the unresolved X-ray emission that remains after the cataloged X-ray point
sources are excised from the ACIS data, in the context of Spitzer and WISE
observations that trace the bubbles, ionization fronts, and photon-dominated
regions that characterize MSFRs. In previous work, they have found that this
unresolved X-ray emission is dominated by hot plasma from massive star wind
shocks. This diffuse X-ray emission is found in every MOXC MSFR, clearly
demonstrating that massive star feedback (and the several-million-degree
plasmas that it generates) is an integral component of MSFR physics.
The Chandra observations used for the Massive Star-forming Regions Omnibus
X-ray Catalog (MOXC) are summarized in Table 2 of the reference paper and
have dates ranging from 2000-04-03 to 2013-01-31 for the 12 MSFRs: the 7
MYStIX targets NGC 6334, NGC 6357, M 16, M 17, W 3, W 4 and NGC 3576, and the
5 "beyond-MYStIX" targets G333.6-0.2, W 51A, G29.96-0.02, NGC 3603 and 30
Doradus.
A similar table to MOXC for other MYStIX targets was presented by Kuhn et al.
(2013, ApJS, 209, 27, available as the HEASARC MYSTIXXRAY table). The main
difference between that table and the MOXC version is that the present
authors have chosen to omit absorption-corrected X-ray source luminosities
from the XPHOT algorithm (Getman et al. 2010, ApJ, 708, 1760) herein, because
those quantities are given in Broos et al. (2013, ApJS, 209, 32, available as
the HEASARC MYSTIXMPCM table) for relevant MYStIX X-ray sources (those
classified as pre-main sequence stars). For beyond-MYStIX targets, the
authors chose to postpone XPHOT calculations until the X-ray sources were
classified, since XPHOT estimates are only appropriate for pre-MS stars. The
XPHOT code is available (Getman et al. 2012, Astrophysics Source Code
Library, record ascl.soft12002) if others wish to use it on MOXC sources.
All photometric quantities in this table are apparent (not corrected for
absorption). The HEASARC has used prefixes 'fb_', 'sb_' and 'hb_' (replacing
the suffixes '_t', '_s' and '_h' used in the reference paper) on the names of
the X-ray photometric quantities which designate the full (total, 0.5 - 8 keV),
soft (0.5 - 2.0 keV) and hard (2-8 keV) energy bands. Correction for finite
extraction apertures is applied to the ancillary reference file (ARF)
calibration products (see Broos et al. 2010, ApJ, 714, 1582, Section 5.3); the
total_counts and counts quantities characterize the extraction and are not
aperture-corrected. The only calibrated quantities presented are the apparent
photon fluxes, in units of photon cm-2 s-1 (see Broos et al. 2010, ApJ,
714, 1582, Section 7.4), and estimates for the apparent energy fluxes, in units
of erg cm-2 s-1 (Getman et al. 2010, ApJ, 708, 1760).
MYSTIXMPCM Catalog
The Massive Young Star-forming complex Study in Infrared and X-rays (MYStIX)
project requires samples of young stars that are likely members of 20 nearby
Galactic massive star-forming regions. Membership is inferred from
statistical classification of X-ray sources, from detection of a robust
infrared excess that is best explained by circumstellar dust in a disk or
infalling envelope and from published spectral types that are unlikely to be
found among field stars. This table contains the MYStIX membership lists,
which total 31,549 probable complex members. In their reference paper, the
authors describe in detail the statistical classification of X-ray sources
via a "Naive Bayes Classifier". These membership lists provide the empirical
foundation for subsequent MYStIX science studies.
The MYStIX project, described by Feigelson et al. (2013, ApJS, 209, 26),
seeks to identify and study samples of young stars in 20 nearby (0.4 < D <
3.6kpc) Galactic massive star-forming regions (MSFRs). These samples are
derived using X-ray data from the Chandra X-ray Observatory, near-infrared
(NIR) photometry from the United Kingdom InfraRed Telescope (UKIRT) and from
the Two Micron All Sky Survey (2MASS), mid-infrared (MIR) photometry from the
Spitzer Space Telescope, and from published spectroscopically-identified
massive stars. The purpose of this study is to describe the authors' efforts
to minimize contaminants in the MYStIX catalogs of young stars. They refer to
these latter objects as the "MYStIX Probable Complex Members" or MPCMs. This
table contains the combined MPCM catalog for all 20 of the MYStIX MSFRs. This
MPCM catalog is the union of three sets of probable members identified by
three different established methods for identifying young stars (see
Feigelson et al. 2013, ApJS, 209, 26, Fig. 3).
Most of the X-ray information on the MPCMs (with the exception of the X-ray
luminosities and absorbing column densities obtained using XPHOT) was
produced by the ACIS Extract (AE) software package (Broos et al. 2010, ApJ,
714, 1582 and 2012, Astrophysics Source Code Library, 1203.001). The AE
software and User's Guide are available at
http://www.astro.psu.edu/xray/acis/acis_analysis.html. X-ray quantities using
the 'fb' prefix are for the full or total energy band from 0.5 - 8.0 keV,
those using the 'sb' prefix are for the soft band from 0.5 - 2.0 keV, and
those using the 'hb' prefix are for the hard band from 2.0 - 8.0 keV. L. K.
Townsley and P. S. Broos (2013, in preparation) and Kuhn et al. (2013, ApJS,
209, 27) identify a few very bright X-ray sources in each region that suffer
from a type of instrumental non-linearity known as photon pile-up
(http://cxc.harvard.edu/ciao/why/pileup_intro.html); X-ray properties
reported for those sources are biased and should be used with caution.
MYSTIXXRAY Catalog
The Massive Young Star-forming complex Study in Infrared and X-ray (MYStIX)
uses data from the Chandra X-Ray Observatory to identify and characterize the
young stellar populations in 20 Galactic (d < 4 kpc) massive star-forming
regions. In this present study, the X-ray analysis for Chandra ACIS-I
observations of 10 of the MYStIX fields is described, and a catalog of >
10,000 X-ray sources is presented in this table. In comparison to other
published Chandra source lists for the same regions, the number of
MYStIX-detected faint X-ray sources in a region is often doubled. While the
higher catalog sensitivity increases the chance of false detections, it also
increases the number of matches to infrared stars. X-ray emitting
contaminants include foreground stars, background stars, and extragalactic
sources. The X-ray properties of sources in these classes are discussed in
the reference paper.
The X-ray observations were made with the imaging array on the Advanced CCD
Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This
array of four CCD detectors subtends 17' x 17' on the sky. The number of
different Chandra pointings for each region, the total exposures for these
pointings, and details of how the observations were taken are provided in
Table 1 of the reference paper. Overall, 29 Chandra ObsIDs are included with
typical integration times for a pointing of 40 - 100 ks, sufficient to detect
most OB stars and lower-mass pre-main-sequence stars down to ~ 0.5 - 1 solar
masses for the MYStIX regions. The 10 MYStIX MSFRs treated herein are listed
in Table 2 of the reference paper.
The data were acquired from the Chandra Data Archive from 2001 Jan to Mar
2008 for 10 MYStIX fields (the Flame Nebula, RCW 36, NGC 2264, the Rosette
Nebula, the Lagoon Nebula, NGC 2362, DR 21, RCW 38, Trifid Nebula and NGC
1893). The X-ray photometry is from Broos et al. (2010, ApJ, 714, 1582; ACIS
Extract); see also the CCCP, Broos et al. (2011, ApJS, 194, 2). The source
significance quantities (fb_prob_no_src, sb_prob_no_src, hb_prob_no_src and
prob_no_src_min) are computed using a subset of each source's extractions
chosen to maximize significance (Broos et al. 2010, ApJ, 714, 1582, Section
6.2). The source position and positional uncertainty quantities are computed
using a subset of each source's extractions chosen to minimize the position
uncertainty (Broos et al. 2010, ApJ, 714, 1582, Sections 6.2 and 7.1). All
other quantities are computed using a subset of each source's extractions
chosen to balance the conflicting goals of minimizing photometric uncertainty
and of avoiding photometric bias (Broos et al. 2010, ApJ, 714, 1582, Sections
6.2 and 7).
The observed and absorption-corrected energy fluxes and their associated
errors and the estimated hydrogen column densities and their uncertainties
are derived using non-parametric procedures (XPHOT, Getman et al. 2010, ApJ,
708, 1760). XPHOT assumes the X-ray spectral shapes of young, low-mass stars,
which come from coronal X-ray emission. XPHOT quantities will therefore be
unreliable for high-mass stars, for which X-ray emission is associated with
the stellar wind.
NAPEXMMCXO Catalog
This table contains some of the results from the first extensive X-ray study
of the North-America and Pelican star-forming region (NGC 7000/IC 5070), with
the aim of finding and characterizing the young population of this cloud.
X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings)
were reduced and source detection algorithm applied to each image. The
authors complement the X-ray data with optical and near-IR data from the
IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and
Spitzer IR data. More than 700 X-ray sources are detected, the majority of
which have an optical or NIR counterpart. This allowed the authors to
identify young stars in different stages of formation. Less than 30% of the
X-ray sources are identified with a previously known young star. the authors
argue that most X-ray sources with an optical or NIR counterpart, except
perhaps for a few tens at near-zero reddening, are likely candidate members
of the star-forming region, on the basis of both their optical and NIR
magnitudes and colors, and of their X-ray properties such as spectral
hardness or flux variations. They are characterized by a wide range of
extinction, and sometimes near-IR excesses, both of which prevent derivation
of accurate stellar parameters. The optical color-magnitude diagram suggests
ages between 1-10 Myr. The X-ray members have a very complex spatial
distribution with some degree of subclustering, qualitatively similar to that
of previously known members. The detailed distribution of X-ray sources
relative to the objects with IR excesses identified with Spitzer is sometimes
suggestive of sequential star formation, especially near the 'Gulf of Mexico'
region, probably triggered by the O5 star which illuminates the whole region.
The authors confirm that around the O5 star no enhancement in the young star
density is found, in agreement with previous results. Thanks to the precision
and depth of the IPHAS and UKIDSS data used, the authors also determine the
local optical-IR reddening law, and compute an updated reddening map of the
entire region.
This table contains the catalog of X-ray sources, with their optical and
near-IR identifications, in the NGC 7000/IC 5070 (North America/Pelican) star
formation complex. The final X-ray source list comprises 721 objects, of
which there are 378 ACIS detections (of which 34 have an XMM-Newton
counterpart), and 343 XMM-Newton-only detection. The chosen detection
threshold, corresponding to approximately one spurious detection per field,
ensures that no more than approximately ten of the 721 detections are
spurious. The 11 XMM-Newton and Chandra fields analyzed in this study are
listed in Tables 1 and 2, respectively, of the reference paper.
NARCSCAT Catalog
This table contains the catalog of 1,415 X-ray sources identified in the
Norma Arm Region Chandra Survey (NARCS), which covers a 2 degree x 0.8 degree
region in the direction of the Norma spiral arm to a depth of ~ 20 ks. Of
these sources, 1,130 are point-like sources detected with >= 3-sigma
confidence in at least one of three energy bands (0.5 - 10, 0.5 - 2, and 2 -
10 keV), five have extended emission, and the remainder are detected at low
significance. Since most sources have too few counts to permit individual
classification, they are divided into five spectral groups defined by their
quantile properties. The authors analyze stacked spectra of X-ray sources
within each group, in conjunction with their fluxes, variability, and
infrared counterparts, to identify the dominant populations in this survey.
They find that ~ 50% of their sources are foreground sources located within 1
- 2 kpc, which is consistent with expectations from previous surveys.
Approximately 20% of sources are likely located in the proximity of the
Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity
of the far Norma arm or beyond. The authors argue that a mixture of magnetic
and non-magnetic cataclysmic variables dominates the Scutum-Crux and near
Norma arms, while intermediate polars and high-mass stars (isolated or in
binaries) dominate the far Norma arm. In the paper, they also present the
cumulative number count distribution for sources in this survey that are
detected in the hard energy band. A population of very hard sources in the
vicinity of the far Norma arm and active galactic nuclei dominate the hard
X-ray emission down to fX ~ 10-14 erg cm-2 s-1, but the distribution
curve flattens at fainter fluxes. The authors find good agreement between the
observed distribution and predictions based on other surveys.
Chandra ACIS-I observations were performed in faint mode of a 2 degree by 0.8
degree region of the Norma spiral arm in 2011 June. This field was subdivided
into 27 pointings; Table 1 in the reference paper reports their coordinates
and exposure times and Figure 1 (op. cit.) is a mosaic image of the survey.
The observing strategy was to cover a wide area with relatively uniform flux
sensitivity and good spatial resolution; therefore, the authors chose field
centers spaced by 12 arcminutes, which provided roughly 70 arcminute2 of
overlap on the outskirts of adjacent observations such that the additional
exposure time in these overlapping regions partly made up for the worsening
point-spread function (PSF) at large off-axis angles.
NGC1068CXO Catalog
This table contains some of the results from a study of the compact X-ray
source population in the Seyfert 2 galaxy NGC 1068, imaged with a 50-ks
Chandra observation. The authors find a total of 84 compact sources on the
ACIS-S3 chip, of which 66 are located within the 25.0 B-mag/arcsec2
isophote of the galactic disk of NGC 1068. In the reference paper, the
spectra of the 21 X-ray sources with at least 50 counts were modeled with
both multicolor disk blackbody and power-law models. The power-law model
provides the better description of the spectrum for 18 of these sources. For
fainter sources, the spectral index was estimated from the hardness ratio.
Five sources have 0.4-8 keV intrinsic luminosities greater than 1039 ergs
s-1, assuming that their emission is isotropic and that they are associated
with NGC 1068. The authors refer to these sources as intermediate-luminosity
X-ray objects (IXOs). If these five sources are X-ray binaries accreting with
luminosities that are both sub-Eddington and isotropic, then the implied
source masses are >~7 solar masses, and so they are inferred to be black
holes. Most of the spectrally modeled sources have spectral shapes similar to
Galactic black hole candidates. However, the brightest compact source in NGC
1068 has a spectrum that is much harder than that found in Galactic black
hole candidates and other IXOs. The brightest source also shows large
amplitude variability on both short-term and long-term timescales, with the
count rate possibly decreasing by a factor of 2 in ~2 ks during this Chandra
observation, and the source flux decreasing by a factor of 5 between this
observation and the grating observations taken just over 9 months later. The
ratio of the number of sources with luminosities greater than 2.1 x 1038
ergs s-1 in the 0.4-8 keV band to the rate of massive (>5 solar masses)
star formation is the same, to within a factor of 2, for NGC 1068, the
Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This
suggests that the rate of production of X-ray binaries per massive star is
approximately the same for galaxies with currently active star formation,
including "starbursts."
The authors were concerned with the study of the discrete X-ray source
population in NGC 1068, imaged within the 8.4 arcmin x 8.4 arcmin (35.3 kpc x
35.3 kpc) field of view of the ACIS S3 chip. Images were extracted from the
reprocessed level 2 events file in soft (0.4-1.5 keV), hard (1.5-5.0 keV) and
full (0.4-5.0 keV) energy bands. The authors used the CIAO program wavdetect
to search the images in the three energy bands for discrete sources of X-ray
emission. They analyzed the images using wavelet scales in the range from 1
pixel (0.492 arcsec) to 16 pixels (7.87 arcsec), separated by a factor of
sqrt(2). The wavelet source detection threshold was set to 10-6, which
gives approximately one false source for the whole S3 chip. The total number
of sources detected by wavdetect in the soft, hard, and full energy band
images was 115, 67, and 138, respectively. Each of these sources was examined
carefully by eye, and only those 84 sources that appear compact to the eye
are included in this source list.
NGC1291CXO Catalog
This table contains some of the results from a study of the X-ray binary
(XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291.
Utilizing the four available Chandra observations totaling an effective
exposure of 179 ks, the authors detect 169 X-ray point sources in the galaxy
in the full band (0.3 - 8.0 keV) with a false-positive probability threshold
of 10-6 (implying approximately 2 false detections given the size of the
image). Of these sources, 75 are in the bulge and 71 are in the ring. The
authors report photometric properties of these sources in a point-source
catalog. There are ~ 40% of the bulge sources and ~ 25% of the ring sources
showing > 3-sigma long-term variability in their X-ray count rate. The X-ray
colors suggest that a significant fraction of the bulge (~ 75%) and ring
(~ 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of
the nuclear source indicate that it is a low-luminosity active galactic
nucleus (AGN) with moderate obscuration; spectral variability is observed
between individual observations. The authors construct 0.3-8.0 keV X-ray
luminosity functions (XLFs) for the bulge and ring XRB populations, taking
into account the detection incompleteness and background AGN contamination.
They reach 90% completeness limits of ~ 1.5 x 1037 and ~ 2.2 x 1037 erg
s-1 for the bulge and ring populations, respectively. Both XLFs can be fit
with a broken power-law model, and the shapes are consistent with those
expected for populations dominated by LMXBs. In the paper, the authors
perform detailed population synthesis modeling of the XRB populations in NGC
1291, which suggests that the observed combined XLF is dominated by an old
LMXB population. They compare the bulge and ring XRB populations, and argue
that the ring XRBs are associated with a younger stellar population than the
bulge sources, based on the relative overdensity of X-ray sources in the
ring, the generally harder X-ray color of the ring sources, the overabundance
of luminous sources in the combined XLF, and the flatter shape of the ring
XLF.
NGC1332CXO Catalog
Chandra ACIS-S3 (Advanced CCD Imaging Spectrometer) observations of the
nearby S0 galaxy NGC 1332 resolve much of the X-ray emission into 73 point
sources, of which 37 lie within the D25 isophote. The remaining galaxy
emission comprises hot, diffuse gas and unresolved sources and is discussed
in two companion papers. The point-source X-ray luminosity function (XLF)
shows the characteristic break seen in other early-type galaxies at ~2 x
1038 ergs s-1. After applying corrections for detection incompleteness at
low luminosities due to source confusion and contamination from diffuse
galactic emission, the break vanishes and the data are well described as a
single power law. This result casts further doubt on there being a
"universal" XLF break in early-type galaxies, marking the division between
neutron star and black hole systems. The logarithmic slope of the
differential XLF (dN/dL), beta = 2.7 +/- 0.5, is marginally (~2.5 sigma)
steeper than has been found for analogous completeness-corrected fits of
other early-type galaxies but closely matches the behavior seen at high
luminosities in these systems. Two of the sources within D25 are
ultraluminous X-ray sources (ULXs), although neither have LX > 2 x 1039
ergs s-1. The absence of very luminous ULXs in early-type galaxies suggests
a break in the XLF slope at ~1-2 x 1039 ergs s-1, although the data were
not of sufficient quality to constrain such a feature in NGC 1332. The
sources have a spatial distribution consistent with the optical light and
display a range of characteristics that are consistent with an LMXB
population. The general spectral characteristics of the individual sources,
as well as the composite source spectra, are in good agreement with
observations of other early-type galaxies, although a small number of highly
absorbed sources are seen. Two sources have very soft spectra, two show
strong variability, indicating compact binary nature, and one source shows
evidence of an extended radial profile. The authors do not detect a central
source in NGC 1332, but find a faint (LX = 2 +/- 1 x 1038 ergs s-1)
point source coincident with the center of the companion dwarf galaxy NGC
1331.
The region of sky containing NGC 1332 was observed with the ACIS instrument
aboard Chandra between 2002 September 19 10:39 and September 20 02:59 UTC for
a nominal ~60 ksec exposure.. This table contains the 73 bona fide X-ray
compact sources detected in this observation, excluding one source centered
within 1" of the galaxy centroid that is actually the central part of the
diffuse galactic emission, one source within the D25 isophote of the
neighboring galaxy NGC 1331, and one source with no photons within the
0.5-7.0 keV band which is likely to be spurious. The spatial extent of 72 of
the 73 sources is consistent with the instrumental PSF. One source (number
14) is clearly more extended than the PSF.
NGC1333CXO Catalog
NGC 1333, a highly active star formation region within the Perseus molecular
cloud complex, has been observed on 2000 July 12.96 - 13.48 with the ACIS-I
detector on board the Chandra X-Ray Observatory. The aim point of the array
was 3 29 06.1, +31 19 38 (J2000,0 RA and Dec), the satellite roll angle was
95.7 degrees, and the effective exposure time after removing time intervals
contaminated by background flaring was 37.8 ks.
In this image with a sensitivity limit in luminosity of ~1028 erg/s for
X-ray sources at the 318 pc distance of NGC 1333, 127 X-ray sources were
detected, most with sub-arcsecond positional accuracy. While 32 of these
sources appear to be foreground stars and extragalactic background objects,
95 X-ray sources are identified with known cluster members. The X-ray
luminosity function of the discovered young stellar object (YSO) population
spans a range of log LX ~= 28.0 - 31.5 erg s-1 in the 0.5 - 8 keV band,
and the absorption column densities range from log NH ~=20 to 23 cm-2.
Most of the sources have plasma temperatures between 0.6 and 3 keV, but a few
sources show higher temperatures up to ~7 keV. Comparison with K-band source
counts indicates that all of the known cluster members with K < 12 and about
half of the members with K > 12 were detected. (K ~= 11, the peak of the
K-band luminosity function, corresponds to 0.2 - 0.4 M_solar stars for a
cluster age of ~1 Myr). Seven of the 20 known YSOs in NGC 1333 which are
producing jets or molecular outflows were detected, as well as one deeply
embedded object without outflows. No evident difference in X-ray emission of
young stars with and without outflows is found.
This present table contains X-ray, optical and near-infrared information on
the 109 X-ray sources that were detected above a source significance
threshold of 1 x 10-6 in any of 3 energy bands: soft: 0.5 - 2.0 keV, hard:
2.0 - 8.0 keV, or full: 0.5 - 8.0 keV, excluding 8 sources that were deemed
to be spurious on visual examination of the images. The faintest on-axis
source emerging from the wavelet detection procedure has 5 extracted counts,
corresponding to a source of log LX ~ 28.0 in the total (0.5 - 8.0 keV)
band for a source with negligible interstellar absorption (AV ~ 1) and a
typical source spectrum of a kT ~ 1 keV thermal plasma. This limit increases
to 28.6 (29.3) if the absorption is increased to AV ~ 5 (10). The
sensitivity decreases by a factor of 4 at the edge of the field compared to
the central regions. 80 of the significant 109 sources (73%) have
counterparts in a non-X-ray band. This table does not include 18 tentative
X-ray sources listed in Table 3 of the reference paper that were found by the
authors by searching for concentrations of photons spatially coincident with
known sources from near-IR, mm/sub-mm, and radio catalogs of this region
which did not reach the detection significance given above. Most of these
tentative sources are believed to be real sources.
NGC1399CXO Catalog
This table contains results from a wide-field study of the globular cluster
(GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC
1399. The large field of view of the Advanced Camera for Surveys/WFC,
combined with the high resolution of the Hubble Space Telescope and Chandra,
allow the authors to constrain the LMXB formation scenarios in elliptical
galaxies. They confirm that NGC 1399 has the highest LMXB fraction in GCs of
all nearby elliptical galaxies studied so far, even though the exact value
depends on galactocentric distance due to the interplay of a differential GC
versus galaxy light distribution and the GC color dependence. In fact, LMXBs
are preferentially hosted by bright, red GCs out to > 5 Reff of the galaxy
light. The finding that GCs hosting LMXBs follow the radial distribution of
their parent GC population argues against the hypothesis that the external
dynamical influence of the galaxy affects the LMXB formation in GCs. On the
other hand, field-LMXBs closely match the host galaxy light, thus indicating
that they are originally formed in situ and not inside GCs. The authors
measure GC structural parameters, finding that the LMXB formation likelihood
is influenced independently by mass, metallicity, and GC structural
parameters. In particular, the GC central density plays a major role in
predicting which GCs host accreting binaries. Finally, this analysis shows
that LMXBs in GCs are marginally brighter than those in the field, and in
particular the only color-confirmed GC with LX > 1039 erg/s shows no
variability, which may indicate a superposition of multiple LMXBs in these
systems.
The optical data were taken with the ACS on board the HST (GO-10129), in the
F606W filter. A detailed description of the HST data and source catalogs are
given in Puzia T.H. et al. 2011, in preparation.
The X-ray data were retrieved from the Chandra public archive (CXC). The
authors selected observations 319 (ACIS-S; 2000 Jan 18) and 1472 (ACIS-I;
2003 May 26).
This table contains the list of 230 X-ray sources detected in the overlap
region common to Chandra ACIS-I, Chandra ACIS-S and HST ACS observation (see
Fig 1 of the reference paper). Details of the X-ray source detection
methodology are given in Section 2.2 of the reference paper.
NGC1600CXO Catalog
The authors observed the X-ray-bright E3 galaxy NGC 1600 and nearby members
of the NGC 1600 group with the Chandra X-Ray Observatory ACIS-S3 to study
their X-ray properties. NGC 1600 is the brightest member of the NGC 1600
group; NGC 1601 (1.6 arcminutes away) and NGC 1603 (2.5 arcminutes away) are
the two nearest galaxies, both of which are non-interacting members. The
authors adopted the 2MASS Point Source Catalog position of J2000.0 RA = 04h
31m 39.87s, Dec = -05o 05' 10.5" as the location of the center of the
NGC 1600 galaxy.
Unresolved emission dominates the Chandra observation; however, some of the
emission is resolved into 71 sources, most of which are low-mass X-ray
binaries associated with NGC 1600. Twenty-one of the sources have LX > 2 x
1039 ergs/s (0.3-10.0 keV; assuming they are at the distance of NGC 1600 of
59.98 Mpc), marking them as ultraluminous X-ray point source (ULX)
candidates. NGC 1600 may have the largest number of ULX candidates in an
early-type galaxy to date; however, cosmic variance in the number of
background active galactic nuclei cannot be ruled out. The spectrum and
luminosity function (LF) of the resolved sources are more consistent with
sources found in other early-type galaxies than with sources found in
star-forming regions of galaxies. The source LF and the spectrum of the
unresolved emission both indicate that there are a large number of unresolved
point sources. The authors propose that these sources are associated with
globular clusters (GCs) and that NGC 1600 has a large GC specific frequency.
Observations of the GC population in NGC 1600 would be very useful for
testing this prediction.
NGC 1600 was observed in two intervals on 2002 September 18-19 (ObsID 4283)
and 2002 September 20 (ObsID 4371) with live exposures of 26,783 and 26,752
s, respectively. The first observation showed clear evidence of a major
background "flare" in the first 20% of the observation. The second
observation had some small fluctuations greater than 20% from the mean rate.
After these were filtered, observations 4283 and 4371 had flare-free exposure
times of 21,562 and 23,616 s, respectively. This table lists all 71 discrete
sources detected by wavdetect over the 0.3-6 keV energy range in the
combination of the two observations. The first 3 sources (source numbers 1, 2
and 3) are clearly extended according to the authors. The authors expect 11
+/- 2 foreground/background sources to be present based on the source counts
in Brandt et al. (2000, AJ, 119, 2349) and Mushotzky et al. (2000, Nature,
404, 459).
The authors determined the observed X-ray hardness ratios for the sources,
using the same techniques that they have used previously. They define three
hardness ratios as H21 = (M-S)/(M+S), H31 = (H-S)/(H+S), and H32 =
(H-M)/(H+M), where S,M, and H are the total counts in the soft (0.3-1 keV),
medium (1-2 keV) and hard (2-6 keV) respectively. From their previous
definitions, they have reduced the hard band from 2-10 to 2-6 keV: since the
6-10 keV range is dominated by background photons for most sources, this
should increase the S/N of the hardness ratio techniques. The hardness ratios
measure observed counts, which are affected by Galactic absorption and
quantum efficiency (QE) degradation in the Chandra ACIS detectors. In order
to compare with other galaxies, it is useful to correct the hardness ratios
for these two soft X-ray absorption effects. Therefore, the authors have
calculated the intrinsic hardness ratios, denoted by a superscript 0, using a
correction factor in each band appropriate to the best-fit spectrum of the
resolved sources, and these are what are quoted in this table.
NGC1893CXO Catalog
The outer Galaxy, where the environmental conditions are different from the
solar neighbourhood, is a laboratory in which it is possible to investigate
the dependence of the star formation process on the environmental parameters.
The authors investigate the X-ray properties of NGC 1893, a young cluster (~
1 - 2 Myr) in the outer part of the Galaxy (galactic radius >= 11 kpc), where
they expect differences in the disk evolution and in the mass distribution of
the stars, so as to explore the X-ray emission of its members and compare it
with that of young stars in star forming regions near to the Sun.
The authors analyze 5 deep Chandra ACIS-I observations with a total exposure
time of 450 ks. Source events of the 1021 X-ray sources have been extracted
with the IDL-based routine ACIS-Extract. Using spectral fitting and quantile
analysis of X-ray spectra, they derive X-ray luminosities and compare the
respective properties of Class II and Class III members. They also evaluate
the variability of sources using the Kolmogorov-Smirnov test and identify
flares in the lightcurves.
The X-ray luminosity of NGC 1893 X-ray members is in the range 1029.5 -
1031.5 erg s-1. Diskless stars are brighter in X-rays than disk-bearing
stars, given the same bolometric luminosity. The authors find that 34% of the
1021 lightcurves appear variable and that they show 0.16 flares per source,
on the average. Comparing their results with those relative to the Orion
Nebula Cluster, they find that, after accounting for observational biases,
the X-ray properties of NGC 1893 and the Orion stars are very similar.
The authors conclude that the X-ray properties of stars in NGC 1893 are not
affected by the environment and that the stellar population in the outer
Galaxy may have the same coronal properties as nearby star-forming regions.
The X-ray luminosity properties and the X-ray luminosity function appear to
be universal and can therefore be used for estimating distances and for
determining stellar properties.
NGC2024CXO Catalog
The NGC 2024 Chandra X-Ray Point Source Catalog contains the results of a
sensitive 76 ks Chandra observation of the young stellar cluster in NGC 2024,
lying at a distance of ~415 pc in the Orion B giant molecular cloud. Previous
infrared observations have shown that this remarkable cluster contains
several hundred embedded young stars, most of which are still surrounded by
circumstellar disks. Thus, it presents a rare opportunity to study X-ray
activity in a large sample of optically invisible protostars and classical T
Tauri stars (CTTSs) undergoing accretion. Chandra detected 283 X-ray sources,
of which 248 were identified with counterparts at other wavelengths, mostly
in the near-infrared. Astrometric registration of Chandra images against the
Two Micron All Sky Survey (2MASS) resulted in positional offsets of ~0.25"
near field center, yielding high confidence identifications of infrared
counterparts. The Chandra detections are characterized by hard, heavily
absorbed spectra and specular variability. Spectral analysis of more than
100 of the brightest X-ray sources yields a mean V-band extinction of ~10.5
magnitudes and typical plasma energies <kT> ~ 3 keV. Chandra detected all but
one of a sample of 27 classical T Tauri stars (CTTSs) identified from
previous near- and mid-infrared photometry, and their X-ray and bolometric
luminosities are correlated. IRS 2b, which is thought to be a massive
embedded late O or early B star that may be the ionizing source of NGC 2024,
is detected as an X-ray source. Seven millimeter-bright cores (FIR 1-7) in
NGC 2024 that may be protostellar were not detected, with the possible
exception of faint emission near the unusual core FIR 4.
NGC2237CXO Catalog
The authors have obtained high spatial resolution Chandra X-ray images of the
NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. They
detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two
Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first
census of the cluster members with 0.2 <~ M <~ 2 Msun. Star locations in
near-infrared color-magnitude diagrams indicate a cluster age of around 2 Myr
with a visual extinction of 1 <~ AV <~ 3 at 1.4 kpc, the distance of the
Rosette Nebula's main cluster NGC 2244. The authors derive the K-band
luminosity function and the X-ray luminosity function of the cluster, which
indicate a population of ~ 400-600 stars. The X-ray-selected sample shows a
K-excess disk frequency of 13%. The young Class II counterparts are aligned
in an arc ~3 pc long suggestive of a triggered formation process induced by
the O stars in NGC 2244. The diskless Class III sources are more dispersed.
Several X-ray emitting stars are located inside the molecular cloud and
around gaseous pillars projecting from the cloud. These stars, together with
a previously unreported optical outflow originating inside the cloud,
indicate that star formation is continuing at a low level and the cluster is
still growing. This X-ray view of young stars on the western side of the
Rosette Nebula complements the authors' earlier studies of the central
cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula.
The large-scale distribution of the clusters and molecular material is
consistent with a scenario in which the rich central NGC 2244 cluster formed
first, and its expanding H II region triggered the formation of the
now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC
2237. A large swept-up shell of material around the H II region is now in a
second phase of collect-and-collapse fragmentation, leading to the recent
formation of subclusters. Other clusters deeper in the molecular cloud appear
unaffected by the Rosette Nebula expansion.
Some sources which have information from published catalogs are listed
by their source_number value below, where for convenience, [OI81] = Ogura &
Ishida (1981, PASJ, 33, 149), [MJD95] = Massey, Johnson, & Degioia-Eastwood
(1995, ApJ, 454, 151) and [BC02] = Berghofer & Christian (2002, A&A, 384, 890):
53 = [OI81] 14 = [MJD95] 104; spectral type B1V; pmRA=11.0 mas/yr,
pmDE=-2.8 mas/yr;
54 = [OI81] 10 = [MJD95] 108; spectral type B2V; pmRA=-2.3 mas/yr,
pmDE=-11.9 mas/yr;
61 = V539 Mon [OI81] 13 = [MJD95] 110; MSX6C G206.1821-02.3456;
pmRA=2.8 mas/yr, pmDE=0.4 mas/yr;
71 = [OI81] 12 = [MJD95] 102; pmRA=6.8 mas/yr, pmDE=0.6 mas/yr;
128 = [OI81] 35 = [MJD95] 471; spectral type A2:; pmRA=-0.8 mas/yr,
pmDE=3.6 mas/yr;
138 = [OI81] 36 = [MJD95] 497; spectral type B5; pmRA=6.5 mas/yr,
pmDE=2.1 mas/yr;
141 = [MJD95] 498; pmRA=-3.0 mas/yr, pmDE=1.9 mas/yr;
149 = [BC02] 11; known X-ray source; log(Lx(ROSAT/PSPC))=31.01 erg/s;
pmRA=0.6 mas/yr, pmDE=-12.6 mas/yr;
161 = [MJD95] 653; pmRA=-1.0 mas/yr, pmDE=-5.4 mas/yr
NGC2244CXO Catalog
This table contains the point source catalog based on the first high spatial
resolution X-ray study of NGC 2244, the 2 Myr old stellar cluster in the
Rosette Nebula, using Chandra. Over 900 X-ray sources are detected within 20
arcminutes of the cluster central position (J2000.0 RA and Dec of 6 31 59.9,
+4 55 36); 77% of these X-ray sources have optical or FLAMINGOS NIR stellar
counterparts and are mostly previously uncataloged young cluster members. The
X-ray-selected population is estimated to be nearly complete between 0.5 and
3 Msolar. A number of further results emerge from the analysis: (1) The
X-ray luminosity function (XLF) and the associated K-band LF indicate a
normal Salpeter IMF for NGC 2244. This is inconsistent with the top-heavy IMF
reported from earlier optical studies that lacked a good census of < 4
Msolar stars. By comparing the NGC 2244 and Orion Nebula Cluster XLFs, the
authors estimate a total population of ~2000 stars in NGC 2244. (2) The
spatial distribution of X-ray stars is strongly concentrated around the
central O5 star, HD 46150. The other early O star, HD 46223, has few
companions. The cluster's stellar radial density profile shows two
distinctive structures: a power-law cusp around HD 46150 that extends to ~0.7
pc, surrounded by an isothermal sphere extending out to 4 pc with core radius
1.2 pc. This double structure, combined with the absence of mass segregation,
indicates that this 2 Myr old cluster is not in dynamical equilibrium. (3)
The fraction of X-ray-selected cluster members with K-band excesses caused by
inner protoplanetary disks is 6%, slightly lower than the 10% disk fraction
estimated from the FLAMINGOS study based on the NIR-selected sample. (4)
X-ray luminosities for 24 stars earlier than B4 confirm the long-standing log
(LX/Lbol) ~ -7 relation. The Rosette OB X-ray spectra are soft and
consistent with the standard model of small-scale shocks in the inner wind of
a single massive star.
NGC2264CX2 Catalog
With the goal of improving the member census of the NGC 2264 star-forming
region and studying the origin of X-ray activity in young pre-main sequence
(PMS) stars, the authors analyzed a deep, 100 ks long, Chandra ACIS
observation covering a 17' x 17' field in the 3 Myr old star-forming region
(SFR) NGC 2264. The preferential detection in X-rays of low-mass PMS stars
gives strong indications of their membership. The authors study X-ray
activity as a function of stellar and circumstellar characteristics by
correlating the X-ray luminosities, temperatures, and absorptions with
optical and near-infrared (NIR) data from the literature.
The authors detected 420 X-ray point sources in the observation above a
4.6-sigma significance threshold using the PWDetect software. Optical and NIR
counterparts were found in the literature for 85% of the sources. The authors
argue that more than 90% of these counterparts are NGC 2264 members, thereby
significantly increasing the known low-mass cluster population by about 100
objects. Among the sources without counterpart, about 50% are probably
associated with members, several of which are expected to be previously
unknown protostellar objects. With regard to activity, several previous
findings are confirmed: X-ray luminosity is related to stellar mass, although
with a large scatter; Lx/Lbol is close to, but almost invariably below,
the saturation level of 10-3, especially when considering the quiescent
X-ray emission. A comparison between classical T Tauri stars (CTTS) and
weak-line T Tauri stars (WTTS) shows several differences: CTTS have, at any
given mass, activity levels that are both lower and more scattered than WTTS;
emission from CTTS may also be more time variable and is on average slightly
harder than for WTTS. However, there is evidence in some CTTS of extremely
cool, ~0.1 - 0.2 keV, plasma which the authors speculate is due to plasma
heated by accretion shocks.
The X-ray spectra of the 199 sources with more than 50 detected photons were
analyzed by the authors. Spectral fits were performed with XSPEC 11.3 and with
several shell and TCL scripts to automate the process. For each source, they
fit the data in the [0.5 - 7.0] keV energy interval with several model spectra:
one and two isothermal components (APEC), subject to photoelectric absorption
from interstellar and circumstellar material (WABS). Plasma abundances for
one-temperature (1T) models were fixed at 0.3 times the solar abundances, while
they were both fixed at that value and treated as a free parameter for the
two-temperature (2T) models. The absorbing column densities, NH, were both
left as a free parameter and fixed at values corresponding to the optically/NIR
determined extinctions, when available: NH = 1.6 x 1021 AV.
This table contains the X-ray, optical and NIR data for the 420 detected X-ray
sources; it does not contain the master catalog of 1598 optical/NIR sources
within the ACIS FOV which was presented in Table 3 of the reference paper,
available at ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/455/903/table3.dat
NGC2264CXO Catalog
The NGC 2264 Chandra X-Ray Point Source Catalog contains the results of a
Chandra observation of a field in the NGC 2264 star-forming region. The
observation was made with Chandra's Advanced CCD Imaging Spectrometer imaging
array (ACIS-I) on 2002 February 9, and has an exposure time of 48.1 ks. The
catalog contains 263 sources, and includes X-ray luminosity, optical and
infrared photometry, and X-ray variability information. The authors found 41
variable sources, 14 of which have a flare-like light curve, and two of which
have a pattern of a steady increase or decrease over a 10-hr period. The
optical and infrared photometry for the stars identified as X-ray sources are
consistent with most of these objects being pre-main sequence stars with ages
younger than 3 Myr.
The authors found that 213 (81%) of the 263 X-ray sources have optical and/or
infrared counterparts, most, but probably not all, of which are likely to be
member stars of NGC 2264. There are 51 X-ray sources that lack optical or
infrared counterparts: the authors believe that these are most likely
extragalactic objects (active galaxies).
NGC2362CXO Catalog
This table contains the results of an observation of the young cluster NGC
2362 in X-rays with Chandra ACIS-I in which 387 point X-ray sources, most of
which are shown to be cluster members, were detected using PWDetect, a
wavelet-based source detection algorithm, with a detection threshold chosen
to ensure no more than one spurious detection in the entire ACIS FOV. The
table lists all of the detected X-ray sources and their basic X-ray
properties, as well as their proposed identifications with optical stars,
using data from Moitinho et al. (2001ApJ...563L..73M; UBVRI photometry) and
Dahm (2005, CDS Cat. <J/AJ/130/1805>; H-alpha data), as well as newer
photometric data from Moitinho et al. (2005, in 'Cores to Clusters' [A&SSL,
324], 167). A matching position of less than 4 times the X-ray positional
uncertainty of the X-ray source from PWDetect was used. Also included in the
table is a classification of the optically-identified X-ray sources, based on
their positions in the HR Diagram, which helps to separate rather clearly the
cluster members from interloping field objects.
NGC2403CX2 Catalog
This table contains a comprehensive X-ray point source catalog of the galaxy
NGC 2403, an outlying member of the M 81 group of galaxies, as part of the
Chandra Local Volume Survey. The combined archival observations of this
galaxy have an effective exposure time of 190 ks. When combined with the
catalogs of sources in NGC 55 and NGC 4214 given in this same reference
paper, and the authors' previously published catalogs for NGC 300 (Binder et
al. 2012, ApJ, 758, 15) and NGC 404 (Binder et al. 2013, ApJ, 763, 128), the
CLVS contains 629 high-significance X-ray sources total down to a limiting
unabsorbed luminosity of ~ 5 x 1035 erg s-1 in the 0.35-8.0 keV band in
each of the five galaxies. In the reference paper, the authors present X-ray
hardness ratios, spectral analysis, radial source distributions, and an
analysis of the temporal variability for the X-ray sources detected at high
significance. To constrain the nature of each X-ray source, they carried out
cross-correlations with multi-wavelength data sets. They searched overlapping
Hubble Space Telescope observations for optical counterparts to their X-ray
detections to provide preliminary classifications for each X-ray source as a
likely X-ray binary, background active galactic nucleus, supernova remnant,
or foreground star.
The authors utilized archival X-ray observations: NGC 2403 was observed by
the Chandra X-Ray Observatory using the ACIS-S array on five occasions for a
total of 190 ks:
Obs. ID Date Eff. Exposure time (ks)
2014 2001 Apr 17 35
4627 2004 Aug 09 31
4628 2004 Aug 23 42
4629 2004 Oct 03 40
4630 2004 Dec 22 42
The iterative source detection strategy that was used is described in Section
2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract (AE) was run a final
time on the source list that was produces after an initial run of wavdetect
followed by several iterations of AE, and the Poisson probability of not
being a source (pns) value was computed in each of the following nine energy
bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0
- 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included in the final NGC 2403
catalog, a source was required to have a pns value less than 4 x 10-6 in
any of the nine energy bands. The final CLVS source catalog for NGC 2403
contains 190 sources.
NGC2403CXO Catalog
Archival Chandra observations are used to study the X-ray emission associated
with star formation in the central region of the nearby (D = 3.2 Mpc, 1
arcminute = 1 kpc) SAB(s)cd galaxy NGC 2403. The distribution of X-ray
emission is compared to the morphology visible at other wavelengths using
complementary Spitzer, Galaxy Evolution Explorer, and ground-based H-alpha
imagery. In general, the brightest X-ray emission is associated with H II
regions and to other star-forming structures, but is more pervasive, existing
also in regions devoid of strong H-alpha and UV emission.
NGC 2403 was observed in full-frame mode with the Chandra ACIS-S on four
occasions for a total of ~ 180 ks, on 2001 Apr 17, 2004 Aug 13, 2004 Oct 03
and 2004 Dec 22. The source-finding tool described by Tennant (2006, AJ, 132,
1372) was applied to all 4 individual data sets and to the merged data set in
order to search for discrete X-ray sources. The search was limited to the
cnetral 6' x 6' (6 kpc x 6 kpc) region and to events within the full Chandra
energy range 0.3-8.0 keV. Fifty eight point sources were detected in the
merged data set with a signal-to-noise ratio (S/N) above 2.8 and with a
minimum of 5 sigma above background uncertainty (corresponding to a detection
limit of 8-10 counts for a typical on-axis source). These sources were listed
in Table 2 of the reference paper and and are contained in the present
HEASARC table. They can be selected by specifying source_type =
'Point Source'.
The X-ray data were also examined to see if there was emission from known
SNRs and H II regions after masking out the afore-mentioned X-ray point
sources (see Section 2.1 of the reference paper for full details). Events
falling within the areas defined by 24 optically identified SNRs that were
imaged on the S3 chip in the first three observations were used to construct
a composite spectrum. This stacked spectrum was fit by an absorbed 1-T APEC
model with the hydrogen column density as a free parameter in XSPEC which was
then used to translate the observed net count rates into X-ray luminosities.
Only 4 or 5 of these SNRs are likely to be 'truely' detected X-ray sources.
The SNRs can be selected in the present HEASARC table by specifying
source_type ='SNR'.
A similar procedure was used to search the X-ray data for the presence of
X-ray emission at the locations of 47 H II regions in NGC 2403. Events
falling within the areas defined by 47 H II regiuons that were imaged on the
S3 chip in the first three observations were used to construct a composite
spectrum. This stacked spectrum was fit by an absorbed 2-T APEC model with
the hydrogen column density as a free parameter in XSPEC which was then used
to translate the observed net count rates into X-ray luminosities. Only the
most X-ray-luminous H II regions are likely to be 'truely' detected X-ray
sources. The H II regions can be selected in the present HEASARC table by
specifying source_type ='HII Region'.
NGC2516CXO Catalog
The NGC 2516 Chandra X-Ray Point Source Catalog is the result of a
comprehensive study of the Chandra X-ray observations of the young open star
cluster NGC 2516. The authors have analyzed eight individual Chandra
observations, comprising 5 ACIS and 3 HRC-I observations. They have combined
these datasets to achieve the greatest sensitivity, reaching down to a
threshold level of log fX = -14.56 (erg/s/cm2), or log LX = 28.69 (erg/s)
at the 387 pc distance of NGC 2516. Out of 284 X-ray sources detected, 155
are identified with photometric cluster members, with very little ambiguity,
another 60 with non-members. There are 4 X-ray sources with two possible
optical identifications (one cluster member and one nonmember for each), with
no obvious choice between the two candidates. These 4 X-ray sources are
listed in this Browse table twice, one for each optical counterpart, hence
there are (284 + 4 =) 288 entries. There remain 73 X-ray sources without an
optical identification with the authors' optical catalog stars.
NGC2808CXO Catalog
This table contains the sources detected in a Chandra X-ray
observation of the Galactic globular cluster NGC 2808, as well as the
corresponding XMM-Newton data for those sources which have XMM-Newton X-ray
counterparts.
Using new Chandra X-ray observations and existing XMM-Newton
X-ray and Hubble Space Telescope far-ultraviolet observations, the authors
aim to detect and identify the faint X-ray sources belonging to NGC 2808 in
order to understand their role in the evolution
of globular clusters. The authors classify the X-ray sources associated with
the cluster by analysing their colors and variability. Previous observations
with XMM-Newton and far-ultraviolet observations with Hubble are
re-investigated to help identify the Chandra sources associated with the
cluster. The authors compare their results to population synthesis models and
observations of other Galactic globular clusters.
NGC 2808 was observed with the Chandra X-ray Observatory Advanced CCD Imaging
Spectrometer-Imager (ACIS-I) on 2007 June 19-21 (28 months after the
XMM-Newton observation referred to the reference paper) for two distinct
exposures of 46 and 11 kiloseconds. The authors detect 113 sources, of which
16 fall inside the half-mass radius of NGC 2808 and are concentrated towards
the cluster core.
NGC2903CXO Catalog
This table contains some of the results from a deep Chandra observation of
the central regions of the late-type barred spiral galaxy NGC 2903. The
Chandra data reveal soft (kTe ~ 0.2 - 0.5 keV) diffuse emission in the
nuclear starburst region and extending ~ 2' (~ 5 kpc) to the north and west
of the nucleus. Much of this soft hot gas is likely to be from local active
star-forming regions; however, besides the nuclear region, the morphology of
hot gas does not strongly correlate with the bar or other known sites of
active star formation. The central ~ 650 pc radius starburst zone exhibits
much higher surface brightness diffuse emission than the surrounding regions
and a harder spectral component in addition to a soft component similar to
the surrounding zones. The authors interpret the hard component as also being
of thermal origin with kTe ~ 3.6 keV and to be directly associated with a
wind fluid produced by supernovae and massive star winds similar to the hard
diffuse emission seen in the starburst galaxy M82. The inferred terminal
velocity for this hard component, ~ 1100 km/s, exceeds the local galaxy
escape velocity suggesting a potential outflow into the halo and possibly
escape from the galaxy gravitational potential. Morphologically, the softer
extended emission from nearby regions does not display an obvious outflow
geometry. However, the column density through which the X-rays are
transmitted is lower in the zone to the west of the nucleus compared to that
from the east and the surface brightness is relatively higher suggesting some
of the soft hot gas originates from above the disk: viewed directly from the
western zone but through the intervening disk of the host galaxy along sight
lines from the eastern zone. There are several point-like sources embedded in
the strong diffuse nuclear emission zone. Their X-ray spectra show them to
likely be compact binaries. None of these detected point sources are
coincident with the mass center of the galaxy and the authors place an upper
limit on the luminosity from any point-like nuclear source o < 2 x 1038
erg/s in the 0.5 - 8.0keV band, which indicates that NGC 2903 lacks an active
galactic nucleus. Heating from the nuclear starburst and a galactic wind may
be responsible for preventing cold gas from accreting onto the galactic
center.
NGC 2903, a nearby (8.9 Mpc, 1" = 43 pc) late-type barred SAB(rs)bc galaxy with
strong circumnuclear star formation, was observed with Chandra using the ACIS-S
instrument in imaging mode on 2010 March 7 (ObsID 11260). The source finding
tool in lextrct (Tennant 2006, AJ, 132, 1372) was applied in the energy range
of 0.5 - 8.0 keV in order to detect point sources inside the D25 isophote.
A total of 92 point-like sources were detected with a signal-to-noise ratio
(S/N) above 2.4 (see Tennant 2006) and with a minimum of 5 counts above the
background uncertainty. This table contains this list of point-like sources.
NGC300CXO Catalog
This table contains the source catalog from a new Chandra ACIS-I observation
of the nearby (2.0 Mpc) SA(s)d spiral galaxy NGC 300 which was obtained as
part of the Chandra Local Volume Survey (CLVS). This 63-ks exposure covers
~88% of the D25 isophote (R ~ 6.3 kpc) and yields a catalog of 95 X-ray
point sources detected at high significance down to a limiting unabsorbed
0.35-8 keV luminosity of ~ 1036 erg/s. Sources were cross-correlated with a
previous XMM-Newton catalog, and the authors find 75 "X-ray transient
candidate" sources that were detected by one observatory, but not the other.
They derive an X-ray scale length of 1.7 +/- 0.2 kpc and a recent star
formation rate of 0.12 Msun/yr in excellent agreement with optical
observations. Deep, multi-color imaging from the Hubble Space Telescope,
covering ~ 32% of this Chandra field, was used to search for optical
counterparts to the X-ray sources, and the authors have developed a new
source classification scheme to determine which sources are likely X-ray
binaries, supernova remnants, and background active galactic nucleus
candidates. In the reference paper, the authors present the X-ray luminosity
functions (XLFs) at different X-ray energies, and find the total NGC 300
X-ray point-source population to be consistent with other late-type galaxies
hosting young stellar populations (<~ 50 Myr). They find that the XLF of
sources associated with older stellar populations has a steeper slope than
the XLF of X-ray sources coinciding with young stellar populations,
consistent with theoretical predictions.
NGC 300 was observed on 2010 September 25 for 63 ks using ACIS-I during the
Chandra X-Ray Observatory Cycle 12, observation ID 12238. The source
detection strategy that was used is described in Section 2.3 of the reference
paper. ACIS-Extract (AE) was run a final time on the source list that was
produces after an initial run of wavdetect followed by several iterations of
AE, and the Poisson probability of not being a source (pns) value was
computed in each of the following nine energy bands: 0.5 - 8.0, 0.5 - 2.0,
2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0 - 8.0, 0.35 - 1.0 and 0.35 -
8.0 keV. To be included in the final NGC 300 catalog, a source was required
to have a pns value less than 4 x 10-6 in any of the nine energy bands; if
only the 0.35 - 8 keV band were considered, ~4% of significant sources would
have been lost. The final CLVS source catalog for NGC 300 contains 95
sources.
NGC3115CXO Catalog
This table contains some of the results from an in-depth study of low-mass
X-ray binaries (LMXBs) detected in the nearby lenticular galaxy NGC 3115
using the Megasecond Chandra X-ray Visionary Project observation (total
exposure time 1.1 Ms). In total the authors found 136 candidate LMXBs in the
field and 49 in globular clusters (GCs) above 2-sigma detection, with 0.3-8
keV luminosity LX ~ 1036 - 1039 erg s-1. Other than 13 transient
candidates, the sources overall have less long-term variability at higher
luminosity, at least at LX >~ 2 x 1037 erg s-1. In order to identify
the nature and spectral state of these sources, the authors compared their
collective spectral properties based on single-component models (a simple
power law or a multicolor disk) with the spectral evolution seen in
representative Galactic LMXBs. The authors found that in the LX vs. photon
index GammaPL and LX versus disk temperature kTMCD plots, most of their
sources fall on a narrow track in which the spectral shape hardens with
increasing luminosity below LX ~ 7 x 1037 erg s-1, but is relatively
constant (GammaPL ~ 1.5 or kTMCD ~ 1.5 keV) above this luminosity, which
is similar to the spectral evolution of Galactic neutron star (NS) LMXBs in
the soft state in the Chandra bandpass. Therefore, the authors identified the
track as the NS LMXB soft-state track and suggested sources with LX <~
1037 erg s-1 as atolls in the soft state and those with LX >~ 1037
erg s-1 as Z sources. Ten other sources (five are transients) displayed
significantly softer spectra and are probably black hole X-ray binaries in
the thermal state. One of them (a persistent source) is in a metal-poor GC.
The 11 Chandra observations of NGC 3115 are listed in Table 1 of the
reference paper. They were made during three epochs: one in 2001,two in 2010,
and nine in 2012. All observations used the imaging array of the AXAF CCD
Imaging Spectrometer (ACIS).
This table contains the properties of the 482 detected point sources in the
merged and single Chandra ACIS observations of NGC 3115 above a 2-sigma
threshold and after eliminating a number of spurious sources associated with
bright streaks on the ACIS-S1 chip and (in one case) on a CCD edge. 469 of
these sources (indicated by values of obs_flag = '0') have a single entry in
this table, based on their properties as derived from all of the available
Chandra data for that position. There are 13 transient sources (having
obs_flag = 'h') for which an additional entry is provided referring to their
properties in the "high state", and based on the combination of their
high-state observations, as shown in Figures 3(a) - 3(d) in the reference
paper. For source number 198, there is a second additional entry provided
referring to its properties in the "low state", and based on the combination
of its low-state observations, as shown in Figure 3(c) in the reference
paper. Thus, there are 496 entries (rows) in this table, i.e., 482 + 13 + 1.
NGC3293CXO Catalog
NGC 3293 is a young stellar cluster at the northwestern periphery of the
Carina Nebula Complex that has remained poorly explored until now. The
authors wanted to characterize the stellar population of NGC 3293 in order to
evaluate key parameters of the cluster population like the age and the mass
function, and to test claims of an abnormal initial mass function (IMF) and a
deficit of <= 2.5*Msun stars. Thus, they performed a deep (71 ksec) X-ray
observation of NGC 3293 with Chandra in which they detected 1026 individual
X-ray point sources. These X-ray data directly probe the low-mass (M <=
2*Msun) stellar population by means of the strong X-ray emission of young
low-mass stars. The authors have identified counterparts for 74% of the X-ray
sources in their deep near-infrared images.
These data clearly show that NGC 3293 hosts a large population of ~ 1*Msun
stars, refuting claims of a lack of M <= 2.5*Msun stars. The analysis of
the color-magnitude diagram suggests an age of ~8-10 Myr for the low-mass
population of the cluster. There are at least 511 X-ray detected stars with
color-magnitude positions that are consistent with young stellar members
within 7 arcminutes from the cluster center. The number ratio of X-ray
detected stars in the 1-2 solar mass range versus the M >= 5*Msun stars
(known from optical spectroscopy) is well consistent with the expectation
from a normal field initial mass function. Most of the early B-type stars and
~20% of the later B-type stars are detected as X-ray sources.
These data shows that NGC 3293 is one of the most populous stellar clusters
in the entire Carina Nebula Complex (only excelled by Tr 14, and very similar
to Tr 16 and Tr 15). The cluster has probably harbored several O-type stars,
the supernova explosions of which may have had an important impact on the
early evolution of the Carina Nebula Complex.
The authors used the Chandra X-ray Observatory to perform a deep pointing of
the cluster NGC 3293 with the Imaging Array of the Chandra Advanced CCD
Imaging Spectrometer (ACIS-I). The 71-ksec observation was performed as an
open time project with ObsID 16648 (PI: T. Preibisch) during Chandra
Observing Cycle 15 in October 2015 (start date: 2015-10-07 T10:14:23, end
date: 2015-10-08 T06:43:28). The imaging array ACIS-I provides a field of
view of 17' x 17' on the sky (which corresponds to a scale of 11.3 x 11.3pc
at the cluster distance of 2.3 kpc), and has a pixel size of 0.492". The
aimpoint of the observation was RA(J2000) = 10h 35m 50.07s, Dec(J2000)
= -58o 14' 00", which is close to the optical center of the cluster (see
Fig. 1 in the reference paper). The pointing roll angle (i.e., the
orientation of the detector with respect to the celestial North direction)
was 140.19o. In addition to ACIS-I, one CCD detector (CCD 7 = S3) of the
spectroscopic array ACIS-S was also operational during this pointing. It
covers an 8.3' x 8.3' area on the sky southwest of the cluster center. While
the ACIS-I chips are front-illuminated (FI), the S3 chip is back-illuminated
(BI), and thus its response extends to energies below that accessible by the
FI chips. This causes a substantially higher level of background in the S3
chip. Furthermore, the PSF is seriously degraded at the rather large off-axis
angles of the S3 chip. These two effects led to a considerably higher
detection limit for point sources in the area covered by the S3 chip compared
to the region covered by the ACIS-I array. Nevertheless, the S3 data were
included in the data analysis and source detection, and contributed four
point sources to the total source list.
At the distance of 2.3 kpc, the expected ACIS point source sensitivity limit
for a three-count detection on-axis in a 71-ks observation corresponds to a
minimum X-ray luminosity of Lx ~ 1029.7 erg s-1 in the 0.5-8.0 keV
energy band, assuming an extinction of AV ~ 1 mag (NH ~ 2 x 1021
cm-2) typical for the stars in the central region of NGC 3293, and a
thermal plasma with kT = 1 keV (which is a typical value for young stars).
Using the empirical relation between X-ray luminosity and stellar mass and
the temporal evolution of X-ray luminosity from the sample of young stars in
the Orion Nebula Cluster, which was very well studied in the Chandra Orion
Ultradeep Project (Preibisch et al. 2005, ApJS, 160, 401; Preibisch &
Feigelson 2005, ApJS, 160, 390), the authors expected to detect ~90% of the ~
1*Msun stars in the central region of the young cluster NGC 3293.
The X-ray properties of the 97 B-type stars in the ACIS-I field towards the
cluster (24 of which are detected as X-ray sources) are not included in this
HEASARC table, but are listed in Table 3 of the reference paper, which is
also reproduced below:
ESL No.* Star Name X-ray Spectral Type X-ray Luminosity (Lx) log (Lx/Lbol)
Src No. erg/s
49 B2.5 V < 4.33e+30 < -5.88
33 HDE 303073 B8 III < 7.15e+30 < -6.31
65 ALS 20075 B5 III-V < 2.12e+30 < -5.88
77 B6-7 V < 1.42e+30 < -5.91
96 ALS 20084 B6-7 III < 9.09e+29 < -5.96
87 47 B5 V 4.62e+30 -5.11
38 B2.5 V < 7.16e+29 < -6.94
68 78 B9 III 4.79e+30
72 B8 IIp < 6.87e+29
69 B5 V < 3.89e+29 < -6.47
22 HDE 303075 B0.5-1.5n < 6.22e+29 < -7.77
109 B5 V < 5.05e+29 < -6.06
93 B6-7 V < 5.16e+29 < -6.17
116 B6-7 V < 4.74e+29 < -5.88
73 B6-7 V < 3.87e+29 < -6.38
10 CPD-57 3500 395 B1 III 7.35e+29 -7.89
121 ALS 20096 B8: III < 4.84e+29
50 B3 Vn < 5.01e+29 < -6.71
2 HD 91943 418 B0.7 Ib 4.11e+30 -8.15
41 V438 Car B2.5 V < 3.94e+29 < -7.21
48 CPD-57 3505 461 B2.5 V 1.39e+30 -6.67
3 CPD-57 3506A 490 B1 III 5.37e+30 -7.63
125 B8 III-V < 8.62e+29 < -5.48
19 V405 Car 523 B1 V 6.77e+29 -7.88
34 CPD-57 3509 535 B2 IIIh 6.71e+29 -7.54
1 HD 91969 542 B0 Iab 2.78e+31 -7.52
106 565 B6-7 V 1.20e+30 -5.54
53 CPD-57 3512 B3 V < 3.61e+29 < -6.70
98 598 B8 III-V 1.31e+30 -5.65
30 CPD-57 3514 601 B2 V 1.99e+30 -6.64
123 604 B8 III 3.79e+30 -4.98
8 HD 91983 626 B1 III 1.36e+30 -7.78
32 CPD-57 3518 B0.5-B1.5 Vn < 1.20e+30 < -7.14
61 B5 V < 3.87e+29 < -6.56
5 CPD-57 3521 679 B1 III 3.45e+30 -7.61
28 CPD-57 3520 B2 V < 4.16e+29 < -7.46
113 B6-7 V < 4.09e+29 < -6.01
11 CPD-57 3526 703 B1: 2.29e+30
6 CPD-57 3526B 710 B1 III 2.29e+30 -7.73
84 B5 V < 3.99e+29 < -6.33
31 CPD-57 3528 B2 V < 1.50e+30 < -6.66
29 CPD-57 3531 B0.5-B1.5 Vn < 5.99e+29 < -7.56
59 B5 III-Vn < 8.23e+29 < -6.61
80 B5 V < 1.31e+30 < -5.98
13 HD 92024 831 B1 III 6.59e+29 -7.82
108 850 B6-7 V 3.65e+30 -5.09
95 884 B6-7 V 1.49e+30 -5.66
67 B3 V < 1.20e+30 < -6.42
97 B6-7 III < 6.34e+29 < -6.01
94 927 B5 V 4.42e+30 -5.35
85 B5 V < 1.47e+30 < -5.80
4 CPD-57 3523 697 B1 III 3.40e+30 -7.57
7 HD 92044 908 B1 III 2.20e+30 -7.94
14 CPD-57 3524A 704 B0.5 IIIn 5.46e+30 -7.27
* The ESL number is the source number of the star as given in Evans et al.
(2005, A&A, 437, 467).
NGC404CXO Catalog
This table contains a comprehensive X-ray point-source catalog of NGC 404,
the closest face-on (inclination angle of 11 degrees) S0 galaxy to the Milky
Way, which was obtained as part of the Chandra Local Volume Survey (CLVS) and
originally published in Binder et al. (2013). A new 97-ks Chandra ACIS-S
observation of NGC 404 was combined with archival observations for a total
exposure of ~123 ks. This survey yields 74 highly significant X-ray point
sources and is sensitive to a limiting unabsorbed luminosity of ~6 x 1035
erg/s in the 0.35-8 keV band. To constrain the nature of each X-ray source,
cross-correlations with multi-wavelength data were generated. The authors
searched overlapping Hubble Space Telescope (HST) observations for optical
counterparts to their X-ray detections, but found only two X-ray sources with
candidate optical counterparts. They found 21 likely low-mass X-ray binaries
(LMXBs), although this number is a lower limit due to the difficulties in
separating LMXBs from background active galactic nuclei (AGN). The X-ray
luminosity functions (XLFs) in both the soft and hard energy bands are
presented in the 2013 reference paper. The XLFs in the soft band (0.5-2 keV)
and the hard band (2-8 keV) have a limiting luminosity at the 90%
completeness limit of 1035 erg/s and 1036 erg/s, respectively,
significantly lower than previous X-ray studies of NGC 404. The authors find
the XLFs to be consistent with those of other X-ray populations dominated by
LMXBs. However, the number of luminous (>1037 erg/s) X-ray sources per unit
stellar mass in NGC 404 is lower than is observed for other galaxies. The
relative lack of luminous XRBs may be due to a population of LMXBs with
main-sequence companions formed during an epoch of elevated star formation
~0.5 Gyr ago.
NGC 404 was observed during Chandra X-Ray Observatory Cycle 12 on 2010
October 21-22 for 97 ks using the ACIS-S array (Obs. ID 12339). The authors
additionally utilized archival observations: NGC 404 was observed on 1999
December 19 (Obs. ID 870) for ~24 ks and on 2000 August 30 (Obs. ID 384) for
~2 ks, both using the ACIS-S array. The authors created images in the
following energy bands (keV): 0.35-8.0, 0.35-1.0, 1.0-2.0, 2.0-8.0 with bin
sizes of 1, 2, 3, and 4.
The iterative source detection strategy that was used is described in Section
2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract (AE) was run a final
time on the source list that was produces after an initial run of wavdetect
followed by several iterations of AE, and the Poisson probability of not
being a source (pns) value was computed in each of the following nine energy
bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0
- 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included in the final NGC 404
catalog, a source was required to have a pns value less than 4 x 10-6 in
any of the nine energy bands. The final CLVS source catalog for NGC 404
contains 74 sources. Given the survey size of these NGC 404 observations,
there are expected to be ~1.6 false sources included in this NGC 404 final
source catalog.
Three HST fields were used to search for optical counterparts for each of the
X-ray sources. One field (labeled "DEEP") was taken as part of the Advanced
Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST, GO-10915;
Dalcanton et al. 2009, ApJS, 183, 67), while the other two shallower fields
(labeled "NE" and "SW") were obtained as part of GO-11986. Details of the HST
data acquisition and data reduction are provided in Williams et al. (2010,
ApJ, 716, 71).
NGC4214CXO Catalog
This table contains a comprehensive X-ray point source catalog of the IAB(s)m
galaxy NGC 4214 similar to the LMC, one of the nearest examples of a
starburst galaxy with a substantial population of Wolf-Rayet stars, as part of
the Chandra Local Volume Survey. The combined archival observations of this
galaxy have an effective exposure time of 79 ks. When combined with the
catalogs of sources in NGC 55 and NGC 2403 given in this same reference
paper, and the authors' previously published catalogs for NGC 300 (Binder et
al. 2012, ApJ, 758, 15) and NGC 404 (Binder et al. 2013, ApJ, 763, 128), the
CLVS contains 629 high-significance X-ray sources total down to a limiting
unabsorbed luminosity of ~ 5 x 1035 erg s-1 in the 0.35-8.0 keV band in
each of the five galaxies. In the reference paper, the authors present X-ray
hardness ratios, spectral analysis, radial source distributions, and an
analysis of the temporal variability for the X-ray sources detected at high
significance. To constrain the nature of each X-ray source, they carried out
cross-correlations with multi-wavelength data sets. They searched overlapping
Hubble Space Telescope observations for optical counterparts to their X-ray
detections to provide preliminary classifications for each X-ray source as a
likely X-ray binary, background active galactic nucleus, supernova remnant,
or foreground star.
The authors utilized archival X-ray observations: NGC 4214 was observed by
the Chandra X-Ray Observatory using the ACIS-S array on three occasions for a
total of 79 ks:
Obs. ID Date Eff. Exposure time (ks)
2030 2001 Oct 16 25
4743 2004 Apr 03 26
5197 2004 Jul 30 28
The iterative source detection strategy that was used is described in Section
2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract (AE) was run a final
time on the source list that was produces after an initial run of wavdetect
followed by several iterations of AE, and the Poisson probability of not
being a source (pns) value was computed in each of the following nine energy
bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0
- 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included in the final NGC 4214
catalog, a source was required to have a pns value less than 4 x 10-6 in
any of the nine energy bands. The final CLVS source catalog for NGC 2403
contains 116 sources.
NGC4278CXO Catalog
This table lists some of the properties of the discrete X-ray sources
detected in the authors' monitoring program of the globular cluster (GC)-rich
elliptical galaxy, NGC 4278, observed with Chandra ACIS-S in six separate
pointings, resulting in a co-added exposure of 458 ks. From this deep
observation, 236 sources have been detected within the region overlapped by
all observations, 180 of which lie within the D25 ellipse angular diameter
of the galaxy. These 236 sources range in X-ray luminosity LX from 3.5 x
1036 erg s-1 (with 3-sigma upper limit <= 1 x 1037 erg s-1) to ~2 x
1040 erg s-1, including the central nuclear source which has been
classified as a LINER. From optical data, 39 X-ray sources have been
determined to be coincident with a GC, these sources tend to have high X-ray
luminosity, with 10 of these sources exhibiting LX > 1 x 1038 erg s-1.
From X-ray source photometry, it has been determined that the majority of the
236 point sources that have well-constrained colors have values that are
consistent with typical low-mass X-ray binary spectra, with 29 of the sources
expected to be background objects from the log N-log S relation. There are
103 sources in this population that exhibit long-term variability, indicating
that they are accreting compact objects. Three of these sources have been
identified as transient candidates, with a further three possible transients.
Spectral variations have also been identified in the majority of the source
population, where a diverse range of variability has been identified,
indicating that there are many different source classes located within this
galaxy.
This HEASARC table contains the master source list (Table 3 of the reference
paper) and the X-ray properties of the sources in the co-added observations
(Table 4 of the reference paper), but not the X-ray properties of the sources
in the 6 individual observations (Tables 5-10 of the reference paper).
The details of the six individual pointings used in this study, e.g., the
Chandra ObsIDs, dates, exposure times and cleaned exposure times, are given
in Table 1 of the reference paper, and repeated here:
Obs. No.OBSID Date Exposure (s) Cleaned Exposure (s)
1 4741 2005 Feb 3 37462.0 37264.5
2 7077 2006 Mar 16 110303.8 107736.7
3 7078 2006 Jul 25 51433.2 48076.2
4 7079 2006 Oct 24 105071.7 102504.6
5 7081 2007 Feb 20 110724.0 107564.5
6 7080 2007 Apr 20 55824.8 54837.5
Total Co-added 470819.5 457984.0
Notes. The pointing OBSID 7181 was taken before OBSID 7080, so to maintain the
time sequence of the exposures these observation numbers have been labeled as
above in the reference paper.
The details of the energy bands and X-ray colors used in this study are
given in Table 2 of the reference paper, and repeated here:
Band/Color Energy Range/Definition
Broad (B) 0.3-8 keV
Soft (S) 0.3-2.5 keV
Hard (H) 2.5-8 keV
Soft 1 (S1) 0.3-0.9 keV
Soft 2 (S2) 0.9-2.5 keV
Conventional broad (Bc) 0.5-8 keV
Conventional soft (Sc) 0.5-2 keV
Conventional hard (Hc) 2-8 keV
Hardness ratio HR (Hc-Sc)/(Hc+Sc)
X-ray color C21 -log(S2) + log(S1) = log(S1/S2)
X-ray color C32 -log(H) + log(S2) = log(S2/H)
NGC4365CXO Catalog
The authors used the Chandra X-Ray Observatory ACIS-S3 to image the
X-ray-faint elliptical galaxy NGC 4365 and the lenticular galaxy NGC 4382.
This table presents only the NGC 4365 results; however, the results for NGC
4382 are also available in a separate table. NGC 4365 was
observed on 2001 June 23 with a live exposure of 40429 s. The observations
resolved much of the X-ray emission into 99 sources for NGC 4365, most of
which are low-mass X-ray binaries (LMXBs) associated with the galaxy. Within
one effective radius of NGC 4365, about 45% of the counts were resolved into
sources, 30% were attributed to unresolved LMXBs, and 25% were attributed to
diffuse gas. The authors identified 18 out of the 37 X-ray sources in a
central field in NGC 4365 with globular clusters.
The authors defined two hardness ratios: HR21 = (M - S)/(M + S) and HR31 = (H
- S)/(H + S), where S, M, and H are the total counts in the soft (0.3 - 1
keV), medium (1 - 2 keV), and hard (2 - 10 keV) bands, respectively.
NGC4382CXO Catalog
The authors used the Chandra X-Ray Observatory ACIS-S3 to image the
X-ray-faint elliptical galaxy NGC 4365 and the lenticular galaxy NGC 4382.
This table presents only the NGC 4382 results; however, the results for NGC
4365 are also available in a separate table. NGC 4382 was
observed on 2001 May 29-30 for 39749 s. The observations resolved much of the
X-ray emission into 58 sources for NGC 4382, most of which are low-mass X-ray
binaries (LMXBs) associated with the galaxy. Within two effective radii of
NGC 4382, about 22% of the counts were resolved into sources, 33% were
attributed to unresolved LMXBs, and 45% were attributed to diffuse gas.
The authors defined two hardness ratios: HR21 = (M - S)/(M + S) and HR31 = (H
- S)/(H + S), where S, M, and H are the total counts in the soft (0.3 - 1
keV), medium (1 - 2 keV), and hard (2 - 10 keV) bands, respectively.
NGC4472CXO Catalog
The Chandra X-Ray Point Source Catalog of the giant elliptical
galaxy NGC 4472 contains the results of a Chandra ACIS-S/Hubble Space
Telescope (HST) study of the point sources of this Virgo Cluster galaxy.
The authors ran WAVDETECT from the CIAO 2.2 software package using
wavelet scales from 1 to 16 pixels spaced by factors of 2, setting a
false-source probability detection threshold of 10^-6, which should yield
an expectation value of slightly less than one false source over the entire
ACIS-S chip. They identify 144 X-ray point sources outside the nuclear region,
72 of which are located within the HST fields. An additional 3 sources are
within 8" of the center of the galaxy and appear to be associated either with
a weak active galactic nucleus or with brightness enhancements in the hot
interstellar gas. One additional source (not included in this table) appears
to be a spurious detection, as WAVDETECT assigns it a count rate of 1.5 counts,
and visual inspection fails to find evidence of a source at that location.
The optical data show 1102 sources whose half-light radii are small enough to
be globular cluster candidates, 829 of which also have colors consistent with
being globular clusters (with only four in the restricted central 10" region).
30 X-ray sources within 0.7" of an optical source with optical colors
consistent with being globular clusters were found. Two additional sources
show optical colors outside the globular cluster color range and are likely to
be either foreground or background objects.
The thirty globular cluster matches are likely to be
low-mass X-ray binaries (LMXBs) associated with the globular clusters,
while ~ 42 of the X-ray sources have no optical counterparts to V <~ 25
and I <~ 24, indicating that they are likely to be predominantly LMXBs
in the field star population with a small amount of possible
contamination from background active galactic nuclei. Thus
approximately 40% of the X-ray sources are in globular clusters
and ~ 4% of the globular clusters contain X-ray sources.
This HEASARC table contains the X-ray data for the above-mentioned 147
detected X-ray sources, and the correlative optical data for the 30 optical
counterparts which have colors consistent with being globular clusters. It does
not contain the data from the full list of optical sources which were given in
Table 2 of the reference paper.
NGC4636CXO Catalog
This catalog lists the X-ray point-source population in the nearby Virgo
elliptical galaxy NGC 4636 from three Chandra X-ray observations. These
observations, totaling ~193 ks after time filtering, were taken with the
Advanced CCD Imaging Camera (ACIS) over a three-year period. Using a wavelet
decomposition detection algorithm, the authors detected 318 individual point
sources. For their analysis, they used a subset of 277 detections with >= net
10 counts (a limiting luminosity of approximately 1.2 x 1037 erg s-1 in
the 0.5-2 keV band, outside the central 1.5 arcminutes bright galaxy core).
This table contains this subset of 277 X-ray sources. The authors discuss the
radial distribution of the point sources. Between 1.5 and 6 arcminutes from
the center, 25% of the sources are likely to be background sources (active
galactic nuclei (AGNs)) and 75% to be low-mass X-ray binaries (LMXBs) within
the galaxy, while at radial distances greater than 6 arcminutes, background
sources (AGN) will dominate the point sources.
The authors explore short and long-term variability (over timescales of 1 day
to three years) for X-ray point sources in this elliptical galaxy. 54 sources
(24%) in the common ACIS fields of view show significant variability between
observations. Of these, 37 are detected with at least 10 net counts in only
one observation and thus may be "transient." In addition, ~10% of the sources
in each observation show significant short-term variability. The cumulative
luminosity function (LF) for the point sources in NGC 4636 can be represented
as a power law of slope Alpha = 1.14 +/- 0.03. The authors do not detect, but
estimate an upper limit of ~4.5 x 1037 erg s-1 to the current X-ray
luminosity of, the historical supernova SN1939A. They find 77 matches between
X-ray point sources and globular cluster (GC) candidates found in deep
optical images of NGC 4636. In the annulus from 1.5 to 6 arcminutes of the
galaxy center, 48 of the 129 X-ray point sources (37%) with >=10 net counts
are matched with GC candidates. Since they expect 25% of these sources to be
background AGN, the percentage matched with GCs could be as high as 50%. Of
these matched sources, the authors find that ~70% are associated with the
redder GC candidates, those that are thought to have near-solar metal
abundance. The fraction of GC candidates with an X-ray point source match
decreases with decreasing GC luminosity. The authors do not find a
correlation between the X-ray luminosities of the matched point sources and
the luminosity or color of the host GC candidates. The LFs of the X-ray point
sources matched with GCs and those that are unmatched have similar slopes
over 1.8 x 1037 erg s-1 <= Lx <= 1 x 1038 erg s-1.
NGC4649CX2 Catalog
This table contains the main X-ray source catalog for the Chandra monitoring
observations of the 16.5-Mpc distant elliptical galaxy, NGC 4649. The galaxy
has been observed with Chandra ACIS-S3 in six separate pointings, reaching a
total exposure of 299 ks. There are 501 X-ray sources detected in the 0.3-8.0
keV band in the merged observation or in one of the six individual
observations; 399 sources are located within the D25 ellipse. The observed
0.3-8.0 keV luminosities of these 501 sources range from 9.3 x 1036 erg
s-1 to 5.4 x 1039 erg s-1. The 90% detection completeness limit within
the D25 ellipse is 5.5 x 1037 erg s-1. Based on the surface density of
background active galactic nuclei (AGNs) and the detection completeness, we
expect ~ 45 background AGNs among the catalog sources (~ 15 within the D25
ellipse). There are nine sources with luminosities greater than 1039 erg
s-1, which are candidates for ultraluminous X-ray sources. The nuclear
source of NGC 4649 is a low-luminosity AGN, with an intrinsic 2.0-8.0 keV
X-ray luminosity of 1.5 x 1038 erg s-1. The X-ray colors suggest that the
majority of the catalog sources are low-mass X-ray binaries (LMXBs). The
authors find that 164 of the 501 X-ray sources show long-term variability,
indicating that they are accreting compact objects, and discover four
transient candidates and another four potential transients. They also
identify 173 X-ray sources (141 within the D25 ellipse) that are associated
with globular clusters (GCs) based on Hubble Space Telescope and ground-based
data; these LMXBs tend to be hosted by red GCs. Although NGC 4649 has a much
larger population of X-ray sources than the structurally similar early-type
galaxies, NGC 3379 and NGC 4278, the X-ray source properties are comparable
in all three systems.
This HEASARC table contains the main Chandra source catalog of the basic
properties of the 501 X-ray detected sources (Table 3 in the reference paper
which includes both sources detected in the merged X-ray image as well as a
number only detected in the individual observations), and also the
information on source counts, hardness ratios and soft and hard X-ray colors
in the merged observation for the same 501 X-ray detected sources (Table 4 in
the reference paper). It does not contain the information on source counts,
hardness ratios and soft and hard X-ray colors for these same sources in the
six individual observations that were contained in Tables 5 - 10 of the
reference paper.
NGC4649CXO Catalog
The authors performed a Chandra X-ray observation of the X-ray bright E2
elliptical galaxy NGC 4649 (M 60). In addition to bright diffuse emission,
they resolved 165 discrete sources, most of which are presumably low-mass
X-ray binaries (LMXBs). As found in previous studies, the luminosity function
of the resolved sources is well-fitted by a broken power law. In NGC 4697 and
NGC 1553, the break luminosity was comparable to the Eddington luminosity of
a 1.4 solar mass neutron star. One possible interpretation of this result is
that those sources with luminosities above the break are accreting black
holes and those below are mainly accreting neutron stars. The total X-ray
spectrum of the resolved sources is well fitted by a hard power law.
NGC 4649 was observed on 2000 April 20 on the ACIS-S3 CCD operated at a
temperature of -120 C and with a frame time of 3.2 s. In addition to the S3
chip, the ACIS chips I2, I3, S1, S2, and S4 were also turned on for the
duration of the observation. Although a number of serendipitous sources were
seen on the other chips, the analysis of NGC 4649 in this paper was based on
data from the S3 chip alone. The total exposure for the S3 chip was 36,780 s.
The discrete X-ray source population on the ACIS S3 image was determined
using a wavelet detection algorithm in the 0.3 - 10.0 keV band, and they were
confirmed with a local cell detection method. The authors used the CIAO,
WAVDETECT, and CELLDETECT programs. The high spatial resolution of Chandra
implies that the sensitivity to point sources is not affected very strongly
by the background. Thus, the source detection was done using the entire
exposure of 36,780 s, including periods with background flares. The wavelet
source detection significance threshold was set at 10-6, which implies that
less than 1 false source (due to a statistical fluctuation in the background)
would be detected in the entire S3 image. This significance threshold
approximately corresponds to requiring that the source flux be determined to
better than 3 sigma.
NGC55CXO Catalog
This table contains a comprehensive X-ray point source catalog of the SB(s)m
galaxy NGC 55, a member of the nearby Sculptor group of galaxies, as part of
the Chandra Local Volume Survey. The combined archival observations of this
galaxy have an effective exposure time of 56.5 ks. When combined with the
catalogs of sources in NGC 2403 and NGC 4214 given in this same reference
paper, and the authors' previously published catalogs for NGC 300 (Binder et
al. 2012, ApJ, 758, 15) and NGC 404 (Binder et al. 2013, ApJ, 763, 128), the
CLVS contains 629 high-significance X-ray sources total down to a limiting
unabsorbed luminosity of ~ 5 x 1035 erg s-1 in the 0.35-8.0 keV band in
each of the five galaxies. In the reference paper, the authors present X-ray
hardness ratios, spectral analysis, radial source distributions, and an
analysis of the temporal variability for the X-ray sources detected at high
significance. To constrain the nature of each X-ray source, they carried out
cross-correlations with multi-wavelength data sets. They searched overlapping
Hubble Space Telescope observations for optical counterparts to their X-ray
detections to provide preliminary classifications for each X-ray source as a
likely X-ray binary, background active galactic nucleus, supernova remnant,
or foreground star.
The authors utilized archival X-ray observations: NGC 55 was observed by the
Chandra X-Ray Observatory on 2001 September 11 for 47 ks using the ACIS-I
array (Obs. ID 2255), and on 2004 June 29 for 9.5 ks using the ACIS-I array
(Obs. ID 4744). The iterative source detection strategy that was used is
described in Section 2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract
(AE) was run a final time on the source list that was produces after an
initial run of wavdetect followed by several iterations of AE, and the
Poisson probability of not being a source (pns) value was computed in each of
the following nine energy bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0,
1.0 - 2.0, 2.0 - 4.0, 4.0 - 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included
in the final NGC 55 catalog, a source was required to have a pns value less
than 4 x 10-6 in any of the nine energy bands. The final CLVS source
catalog for NGC 55 contains 154 sources.
NGC5866CXO Catalog
S0 galaxies are often thought to be passively evolved from spirals after star
formation is quenched. To explore what is actually occurring in such
galaxies, the authors conducted a multi-wavelength case study of NGC 5866 - a
nearby edge-on S0 galaxy in a relatively isolated environment. This study
shows strong evidence for dynamic activities in the interstellar medium,
which are most likely driven by supernova explosions in the galactic disk and
bulge. Understanding these activities can have strong implications for
studying the evolution of such galaxies. The authors utilized Chandra, Hubble
Space Telescope, and Spitzer data as well as ground-based observations to
characterize the content, structure, and physical state of the medium and its
interplay with the stellar component in NGC 5866. These reveal the presence
of diffuse X-ray-emitting hot gas, which extends as far as 3.5 kpc away from
the galactic plane and can be heated easily by Type Ia SNe in the bulge.
The Chandra/ACIS observation of NGC 5866 was taken on 2002 November 14. The
authors reprocessed the archived data for their study. See Figure 1 in the
reference paper for the Chandra/ACIS-S image of NGC 5866 in the 0.3-7 keV
band. This table contains the detected X-ray point sources listed in table 2
of this paper.
NGC6231CX2 Catalog
NGC 6231 is a young cluster (age ~2-7 Myr) dominating the Sco OB1 association
(distance ~1.59 kpc) with ~100 O and B stars and a large pre-main-sequence
stellar population. The authors combine a reanalysis of archival Chandra
X-ray data with multi-epoch near-infrared (NIR) photometry from the VISTA
Variables in the Via Lactea (VVV) survey and published optical catalogs to
obtain a catalog of 2148 probable cluster members. This catalog is 70% larger
than previous censuses of probable cluster members in NGC 6231. It includes
many low-mass stars detected in the NIR but not in the optical and some B
stars without previously noted X-ray counterparts. In addition, the authors
identify 295 NIR variables, about half of which are expected to be
pre-main-sequence stars. With the more complete sample, they estimate a total
population in the Chandra field of 5700-7500 cluster members down to 0.08
Msun (assuming a universal initial mass function) with a completeness
limit at 0.5 Msun. A decrease in stellar X-ray luminosities is noted
relative to other younger clusters. However, within the cluster, there is
little variation in the distribution of X-ray luminosities for ages less than
5 Myr. The X-ray spectral hardness for B stars may be useful for
distinguishing between early-B stars with X-rays generated in stellar winds
and B-star systems with X-rays from a pre-main-sequence companion (>35% of B
stars). A small fraction of catalog members have unusually high X-ray median
energies or reddened NIR colors, which might be explained by absorption from
thick or edge-on disks or being background field stars.
This work makes use of some basic cluster properties available from the
literature. Summaries of older studies are provided by Sana et al. (2006,
J/A+A/454/1047), available in
NGC6231XMM, and Reipurth
(2008hsf2.book.....R). Expanded catalogs of cluster members have been
provided by Sung et al. (2013, J/AJ/145/37) and Damiani et al. 2016,
J/A+A/596/A82 (DMS2016), available at
NGC6231CXO.
Chandra X-ray observations were made using the imaging array on the Advanced
CCD Imaging Spectrometer (ACIS-I; Garmire et al. 2003SPIE.4851...28G). This
instrument is an array of four CCD detectors that subtends 17'x17'. The
target was observed in 2005 July (Sequence 200307; PI: S. Murray) in two
observations (ObsID 5372 and 6291), and the data were retrieved from the
Chandra Data Archive.
The NIR ZYJHKs data were obtained from the VVV survey (Minniti et al.
2010NewA...15..433M; Saito et al. 2012, Cat. II/337). VVV is a multi-epoch NIR
survey that covers both the Galactic bulge and an adjacent Galactic disk
region and was carried out using the 4.1 m VISTA telescope on Cerro Paranal.
The VVV data were taken with the VISTA Infrared CAMera (VIRCAM; Dalton et al.
2006SPIE.6269E..0XD), a 4x4 array of Raytheon VIRGO 2048x2048 20 micron pixel
detectors with a pixel scale of 0.34".
In addition to the VVV photometry, public optical or infrared catalogs are
available from surveys and publications. We have included VPHAS+ photometry
(Drew et al. 2014, J/MNRAS/440/2036), UBVRI (Johnson-Cousins system) and
H-alpha photometry from Sung et al. (2013, J/AJ/145/37), and Spitzer/IRAC
photometry from the GLIMPSE survey (Benjamin et al. 2003, Cat. II/293).
NGC6231CXO Catalog
NGC 6231 is a massive young star cluster, near the center of the Sco OB1
association. While its OB members are well studied, its low-mass population
has received little attention. In the reference paper, the authors present
high-spatial resolution Chandra ACIS-I X-ray data, wherein they detect 1,613
point X-ray sources. Their main aim was to clarify the global properties of
NGC 6231 down to low masses through a detailed membership assessment, and to
study the cluster stars' spatial distribution, the origin of their X-ray
emission, the cluster age and formation history, and its initial mass
function.
The authors use X-ray data, complemented by optical and IR data, to establish
cluster membership. The spatial distribution of different stellar subgroups
also provides highly significant constraints on cluster membership, as does
the distribution of X-ray hardness. In their study, the authors perform
spectral modeling of group-stacked X-ray source spectra.
The X-ray properties of the sources detected in the Chandra observations of
NGC 6231, and their cross-identifications in the catalogs of Sung, Sana, and
Bessell (2013 AJ, 145, 37; hereafter SSB); VPHAS+ (Drew et al., 2014, MNRAS,
440, 2036); and 2MASS (CDS Cat. II/246), and information about membership,
H-alpha or IR excess, mass and luminosity are also provided. SSB derive a
distance modulus for NGC 6231 of 11.0 (1,585 pc), a reddening E(B - V) =
0.47, and a nearly normal reddening law with R = 3.2. The present authors
adopt these values for this work.
NGC 6231 was observed twice in X-rays with the ACIS-I detector on-board the
Chandra X-ray Observatory on 2005, July 3 to 4 (ObsId 5372) and 16 to 17
(ObsID 6291), respectively. The two pointings share the same center
(aimpoint) but were performed with a different roll angle. Effective exposure
times for the observations were 76.19 and 44.39 ks, respectively, making the
total exposure time 120.58 ks. The data were filtered to retain the energy
band 0.3 - 8.0 keV, and the full-field lightcurves were inspected to search
for high-background periods, but none were found. Exposure maps were computed
using standard CIAO software tasks. To these prepared datasets, the authors
applied the source detection software PWDetect, a wavelet-based detection
algorithm developed at INAF-Osservatorio Astronomico di Palermo. The PWDetect
version used here is a modified one, able to detect sources in combined
datasets, thus taking full advantage of the deep total exposure. The
detection threshold was chosen such as to yield ten spurious detections in
the field of view (FOV), for the given background counts. This is a more
relaxed constraint than the more usual limit of one spurious detection per
field, but is justified when the lowered threshold allows the detection of
more than one hundred additional faint sources, as it was the case here or in
the COUP Program's Orion data.
This HEASARC table contains the list of 1,613 detected X-ray point sources
and information about their optical and IR counterparts, where known. It does
not contain the 275 additional candidate cluster members (where their
candidacy was based on their having H-alpha or IR excesses) which lack X-ray
counterparts and that were also listed in Table B.2 of the reference paper.
NGC6334CXO Catalog
The full stellar population of NGC 6334, one of the most
spectacular regions of massive star formation in the nearby Galaxy, has not
been well sampled in past studies. The authors have analyzed a mosaic of two
Chandra X-ray Observatory images of the region using sensitive data analysis
methods, giving a list of 1607 faint X-ray sources with arcsecond positions
and approximate line-of-sight absorption. About 95% of these are expected to
be cluster members, most lower mass pre-main-sequence stars. Extrapolating to
low X-ray levels, the total stellar population is estimated to be 20,000 -
30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial
pattern with ~10 distinct star clusters. The heavily obscured clusters are
mostly associated with previously known far-infrared sources and radio H II
regions. The lightly obscured clusters are mostly newly identified in the
X-ray images. Dozens of likely OB stars are found, both in clusters and
dispersed throughout the region, suggesting that star formation in the complex
has proceeded over millions of years. A number of extraordinarily heavily
absorbed X-ray sources are associated with the active regions of star
formation.
NGC6357CXO Catalog
This contains some of the results from the first high spatial resolution
X-ray study of the massive star-forming region NGC 6357, which were obtained
in a 38 ks Chandra/ACIS observation. Inside the brightest constituent of this
large H II region complex is the massive open cluster Pismis 24. It contains
two of the brightest and bluest stars known, yet remains poorly studied; only
a handful of optically bright stellar members have been identified. The
authors have investigated the cluster extent and initial mass function and
detected ~800 X-ray sources with a limiting sensitivity of ~ 1030 erg
s-1: this provides the first reliable probe of the rich intermediate-mass
and low-mass population of this massive cluster, increasing the number of
known members from optical studies by a factor of ~ 50. The high-luminosity
end (log L[2-8 keV] >= 30.3 erg s-1) of the observed X-ray luminosity
function in NGC 6357 is clearly consistent with a power-law relation as seen
in the Orion Nebula Cluster and Cepheus B, yielding the first estimate of NGC
6357's total cluster population, a few times the known Orion population. The
long-standing LX ~ 10-7 Lbol correlation for O stars is confirmed.
Twenty-four candidate O stars and one possible new obscured massive YSO or
Wolf-Rayet star are presented. Many cluster members are estimated to be
intermediate-mass stars from available infrared photometry (assuming an age
of ~ 1 Myr), but only a few exhibit K-band excess. The authors report the
first detection of X-ray emission from an evaporating gaseous globule at the
tip of a molecular pillar; this source is likely a B0-B2 protostar.
NGC 6357 was observed on 2004 July 9 with the Imaging Array of the Advanced
CCD Imaging Spectrometer (ACIS-I) on board Chandra. Four front-illuminated
(FI) CCDs form the ACIS-I, which covers a field of view (FOV) of ~ 17 by 17
arcminutes. The observation was made in the standard Timed Exposure, Very
Faint mode, with 3.2 s integration time and 5 pixel by 5 pixel event islands.
The total exposure time was 38 ks and the satellite roll angle was 289
degrees. The aim point was centered on the O3 If star Pis 24-1, the heart of
the OB association Pismis 24. The Chandra observation ID is 4477.
Data reduction started with filtering the Level 1 event list processed by the
Chandra X-ray Center pipeline to recover an improved Level 2 event list. To
improve absolute astrometry, X-ray positions of ACIS-I sources were obtained
by running the wavdetect wavelet-based source detection algorithm within the
Chandra Interactive Analysis of Observations (CIAO) package on the original
Level 2 event list, using only the central 8 by 8 arcminutes of the field.
The resulting X-ray sources were matched to the 2MASS point source catalog.
The authors calculated the position offsets between 277 X-ray sources and
their NIR counterparts and applied an offset of +0.02" in right ascension
(R.A.) and -0.33" in declination to the X-ray coordinates.
From an initial list of 910 potential X-ray sources, the authors rejected
sources with a PB > 1% likelihood of being a background fluctuation. The
trimmed source list includes 779 sources, with full-band (0.5 - 8.0 keV) net
(background-subtracted) counts ranging from 1.7 to 1837 counts. The 779 valid
sources were purposely divided by the authors into two lists: the 665 sources
with PB < 0.1% make up the primary source list of highly reliable sources
(Table 1 in the reference paper; sources with source_type = 'M' in this
table), and the remaining 114 sources with PB >= 0.1% likelihood of being
spurious background fluctuations were listed as tentative sources in Table 2
of the reference paper (source_type = 'T' in this table). The authors believe
that most of these tentative sources are likely real detections.
NGC6357OID Catalog
Circumstellar disks are expected to evolve quickly in massive young clusters
harboring many OB-type stars. Two processes have been proposed to drive the
disk evolution in such cruel environments: (1) gravitational interaction
between circumstellar disks and nearby passing stars (stellar encounters),
and (2) photoevaporation by UV photons from massive stars. The relative
importance of both mechanisms is not well understood. Studies of massive
young star clusters can provide observational constraints on the processes of
driving disk evolution.
The authors investigate the properties of young stars and their disks in the
NGC 6357 complex, concentrating on the most massive star cluster within the
complex: Pismis 24. They use infrared data from the 2MASS and Spitzer GLIMPSE
surveys, complemented with their own deep Spitzer imaging of the central
regions of Pismis 24, in combination with X-ray data to search for young
stellar objects (YSOs) in the NGC 6357 complex. The infrared data constrain
the disk presence and are complemented by optical photometric and
spectroscopic observations, obtained with VLT/VIMOS, that constrain the
properties of the central stars. For those stars with reliable spectral
types, they combine spectra and photometry to estimate the masses and ages.
For cluster members without reliable spectral types, they obtain the mass and
age probability distributions from R and I-band photometry, assuming these
stars have the same extinction distribution as those in the "spectroscopic"
sample. The authors compare the disk properties in the Pismis 24 cluster with
those in other clusters/star-forming regions employing infrared color-color
diagrams.
The authors discover two new young clusters in the NGC 6357 complex. They give
a revised distance estimate for Pismis 24 of 1.7 +/- 0.2 kpc. They also find
that the massive star Pis 24-18 is a binary system, with the secondary being
the main X-ray source of the pair. The authors provide photometry in 9 bands
between 0.55 and 8 micron (µm) for the members of the Pismis 24 cluster. They
derive the cluster mass function and find that up to the completeness limit at
low masses it agrees well with the initial mass function of the Trapezium
cluster. They derive a median age of 1 Myr for the Pismis 24 cluster members.
The R-band observations were performed on 2008 April 1 and 6, and the I-band
observations were done on 2008 May 1, both using the VIMOS instrument on the
VLT. The near-IR photometry in the J, H and Ks bands were taken from the
2MASS. The mid-IR photometry at 3.6, 4.5, 5.8 and 8.0 um were obtained withe
the Spitzer IRAC camera, both from the GLIMPSE I survey and from deep
observations of the central Pismis 24 region carried out by the authors on
2006 September 29. The X-ray observations were made by the Chandra ACIS-I
instrument and previously published by Wang et al. (2007, ApJS, 168, 100: the
HEASARC NGC6357CXO table). The X-ray sources were matched to sources detected
in the VIMOS R and I bands based on positional coincidence, using a 1.5
arcseconds tolerance. The accuracy of the optical and X-ray positions was 0.6
and 1.0 arcseconds, respectively. Given the high space density of sources in
the central regions of Pismis 24, there may be a substantial number (up to
1/6 of the sources) of "false positives", according to the authors.
This table contains the list of 643 optical/IR counterparts to the Chandra
X-ray sources found by Wang et al. (2007) which were identified by the
present authors: for 136 of the 779 X-ray sources, no counterparts were
found.
NGC6530CXO Catalog
In a deep 60 ks Chandra ACIS-I X-ray observation of the very young
(~ 1.5 - 2.0 Myr) cluster NGC 6530 on 2001 Jun 18-19, the authors have detected
884 X-ray point sources and argue that a very large fraction of them (90%-95%)
must be pre-main-sequence (PMS) cluster members, mostly low-mass stars. This is
a significant enlargement of the known NGC 6530 stellar population with respect
to previous optical studies, including H-alpha surveys. They identify 220
X-ray sources with catalogued stars down to V = 17, while most unidentified
sources have fainter counterparts. Moreover, they find an infrared counterpart
in the 2MASS (CDS. No. <II/246>) Catalog for 731 X-ray sources. The optically
identified cluster X-ray sources are found in a band in the H-R diagram above
the main sequence, in the locus of 0.5 - 1.5 Myr PMS stars, with masses down
to 0.5 - 1.5 solar masses (M_sun).
The pointing direction for the Chandra observation was the NGC 6530 cluster
center at RA = 18^h 04^m 24.38^s, Dec = -24^o 21' 05.8" (J2000.0). The PWDetect
algorithm found 884 X-ray point sources in the ACIS-I image above a detection
significance threshold chosen to ensure only 1 spurious detection on the
average. The Sung et al. (2000, AJ, 120, 333; CDS Cat. <J/AJ/120/333>) = SCB
Catalog of optical objects against which the X-ray point source list was
compared doed not cover the easternmost 2.25' of the ACIS FOV (RAs later than
18^h 04^m 52^s), notice, which comprises about 13% of the ACIS FOV. There are
46 detected X-ray sources (5.2% of the total) in the area not covered by the
SCB Catalog. A matching distance of 4 times the X-ray error radius or 2.0"
(whichever is greater) was used to identify optical counterparts to the X-ray
sources, after a systematic shift between the X-ray and optical positions of
-0.4" and 1.84" in RA and declination, respectively, was applied. The authors
estimate that as many as 28 of their 220 optical identifications may be
spurious, preferentially those in the outer parts of the FOV where the
positional uncertainties are larger.
There are 8792 'good' 2MASS sources in the ACIS FOV. A matching distance of
4 times the X-ray error radius or 1.5" (whichever is greater) was used to
identify 2MASS counterparts to the X-ray sources, after systematic
corrections of 0.3" and 1.75" in RA and declination, respectively, were
applied to the 'raw' X-ray positions. There are 13 cases where there are two
possible IR counterparts to a single X-ray source, and 2 cases where there
are three possible IR Counterparts to a single X-ray source. (Notice that, in
such cases, this table contains multiple entries, one for each counterpart,
and hence there are 901 entries compared to 884 X-ray sources.) The authors
conclude that the plausible number of spurious X-ray-2MASS identifications is
between 30 and 50. Overall, there remain 146 X-ray sources with no optical or
IR identification.
NGC6530OID Catalog
The authors have obtained astrometry and BVI photometry, down to
a V magnitude of ~22, of the very young open cluster NGC 6530, from
observations taken with the Wide Field Imager (WFI) camera at the MPG/ESO 2.2m
Telescope. They have positionally matched their optical catalog with the list
of X-ray sources found in a Chandra-ACIS observation of this cluster (Damiani
et al. 2004, ApJ, 608, 781: available in Browse both via links from this table
and also as the NGC6530CXO table), finding a total of 828 stars in common, 90%
of which are pre-main sequence stars in NGC 6530.
The data used in this work come from the combination of optical BVI
images taken with the WFI camera made on 27-28 July 2000, a 60 ks Chandra
ACIS X-ray observation, and public near-infrared data from the All-Sky
Catalog of Point Sources of the Two Micron All Sky Survey (2MASS, CDS Cat.
<II/24>).
The total number of optical sources falling in the Chandra FOV is 8956,
while the Damiani et al. (2004, ApJ, 608, 781) Catalog contains 884 X-ray
sources, who concluded that at least 90% of the X-ray sources are very
probable cluster members. To cross-correlate the X-ray and optical catalogs,
the authors used a matching distance of < 4 sigmaX, where sigmaX is the
the X-ray positional error, or 1.5", whichever is smaller, after a systematic
shift between the X-ray and WFI positions of 0.2" in RA and -0.26" in Dec
had been included. This resulted in a number of multiple identifications,
among which 4 turned into unique identifications when a reduced distance of
1.5" was used. This finally resulted in 721 single, 44 double, and 3 triple
identifications in the optical catalog; in addition, one X-ray source has
4 optical identifications, and another has 6 optical identifications.
The total number of X-ray sources with WFI counterparts is therefore 770;
of them, only 15 X-ray identified stars come from the Sung et al. (2000,
AJ, 120, 333) Catalog and are not in the WFI Catalog. The total number
of optical sources with an X-ray counterpart is 828. The agreement between
X-ray and WFI optical positions is excellent in most cases, with offsets
below 1".
NGC6791CXO Catalog
This table contains some of the results from the first X-ray study of NGC
6791, one of the oldest open clusters known (8 Gyr). This Chandra observation
was aimed at uncovering the population of close interacting binaries down to
an X-ray luminosity (LX) of ~1 x 1030 erg/s (0.3-7 keV). The authors
detect 86 sources within 8 arcminutes of the cluster center, including 59
inside the half-mass radius of 4.42 arcminutes. centered on 19h 20m
53s, +37o 46' 18" (J2000.0). They identify 20 sources with proper-motion
cluster members, which are a mix of cataclysmic variables (CVs), active
binaries (ABs), and binaries containing sub-subgiants. With follow-up optical
spectroscopy, the authors confirm the nature of one CV. They also discover
one new, X-ray variable candidate CV with Balmer and He II emission lines in
its optical spectrum; this is the first X-ray-selected CV in an open cluster.
The number of CVs per unit mass is consistent with the field, suggesting that
the 3-4 CVs observed in NGC 6791 are primordial. The authors compare the
X-ray properties of NGC 6791 with those of a few old open clusters (NGC 6819,
M67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number
of ABs brighter than 1 x 1030 erg/s normalized by cluster mass is lower in
NGC 6791 than in M 67 by a factor ~3-7. CVs, ABs, and sub-subgiants brighter
than 1 x 1030 erg/s are under-represented per unit mass in the globular
clusters compared to the oldest open clusters, and this accounts for the
lower total X-ray luminosity per unit mass of the former. This indicates that
the net effect of dynamical encounters may be the destruction of even some of
the hardest (i.e., X-ray-emitting) binaries.
The authors observed NGC 6791 with the Advanced CCD Imaging Spectrometer
(ACIS) on Chandra from 2004 July 1 20:51 UTC until July 2 10:49 UTC for a
total exposure time of 48.2ks (ObsID 4510). They obtained low-resolution
spectra of candidate optical counterparts to guide the classification of the
X-ray sources. A total of 16 candidate counterparts brighter than V ~18.3
were observed with the FAST long-slit spectrograph on the 1.5m Tillinghast
telescope on Mt. Hopkins on nine nights between 2005 June 7 to September 2
(coverage from 3480 to 7400 Angstrom and a 3 Angstrom resolution). Candidate
optical counterparts fainter than V ~17 were observed with the fiber-fed
multi-object spectrograph Hectospec on the 6.5m Multi-Mirror Telescope. A
total of 16 candidate counterparts were observed on the nights of 2005 May 13
and July 4-6 (spectra that cover 3700 to 9150 Angstrom with a 6-Angstrom
resolution).
The authors performed source detections in broad (0.3-7.0 keV), soft (0.3-2.0
keV) and hard (2.0-7.0 keV) energy bands, also used in their Chandra study of
M 67 (van den Berg et al. 2004, A&A, 418. 509), so as to facilitate
comparison. The CIAO detection routine wavdetect was run for scales of 1.0 to
11.3 pixels, in steps increasing by a factor of sqrt(2), with the larger
scales appropriate for large off-axis angles where the point-spread function
(PSF) becomes significantly broader. The authors computed exposure maps for
the response at 1 keV to account for spatial variations of the sensitivity.
The wavdetect detection threshold was set to 10-6, from which the authors
expect two spurious detections per detection scale (so 16 spurious detections
in total) in the area that they consider here. Combination of the broad,
soft, and hard-band source lists results in a master catalog of 86 distinct
sources within 8 arcmin of the cluster center, of which 59 lie inside the
half-mass radius rh. To investigate the validity of the sources, the
authors also ran wavdetect with a threshold of 10-7 or an expected number
of spurious sources of 1.6. The 14 sources not detected in this run are
marked with a value of the source_flag parameter of 'T' in this table
(replacing the '*' symbol used in the original table).
NGC752CXO Catalog
This table provides a list of X-ray sources detected in a ~140 ks Chandra
X-ray observation of the open cluster NGC 752. For the sources with 2MASS
counterparts, the values of their magnitudes in the J, H and K bands are also
given.
Very little is known about the evolution of stellar activity between the ages
of the Hyades (0.8 Gyr) and the Sun (4.6 Gyr). To gain information on the
typical level of coronal activity at a star's intermediate age, the authors
have studied the X-ray emission from stars in the 1.9 Gyr-old open cluster
NGC 752. They analyzed a ~ 140 ks Chandra observation of NGC 752 and a ~50 ks
XMM-Newton observation of the same cluster. They detected 262 X-ray sources
in the Chandra data and 145 sources in the XMM-Newton observation. Around 90%
of the catalogued cluster members within Chandrás field of view are detected
in the X-ray observation. The X-ray luminosity of all observed cluster
members (28 stars) and of 11 cluster member candidates was derived. These
data indicate that, at an age of 1.9 Gyr, the typical X-ray luminosity Lx
of the cluster members with masses of 0.8 to 1.2 solar masses is 1.3 x 1028
erg s-1, which is approximately a factor of 6 times less intense than that
observed in the younger Hyades. Given that Lx is proportional to the square
of a star's rotational rate, the median Lx of NGC 752 is consistent, for t
>= 1 Gyr, with a decaying rate in rotational velocities vrot ~ t-alpha
with alpha ~ 0.75, steeper than the Skumanich relation (alpha ~ 0.5) and
significantly steeper than that observed between the Pleiades and the Hyades
(where alpha <0.3), suggesting that a change in the rotational regimes of the
stellar interiors is taking place at an age of ~ 1 Gyr.
The 135 ks observation of NGC 752 was performed by the Chandra ACIS camera on
September 29, 2003 starting at 21:11:59 UT. The X-ray source detection was
performed on the event list using the Wavelet Transform detection algorithm
developed at Palermo Astronomical Observatory PWDETECT, available at
http://oapa.astropa.unipa.it/progetti_ricerca/PWDetect. Initially, the energy
range 0.2 - 10 keV was selected and the threshold for source detection was
taken as to ensure a maximum of 1-2 spurious sources per field. 169 sources
were detected in this way. The analysis of these sources hardness ratios
showed, however, that all the catalogued stars in the field had low hardness
ratios, HR < ~ 0.2, where HR is the number of photons in the 2 - 8 keV band
over the number in the 0.5 - 2 keV band. Thus, to maximize the detection of
stellar sources, PWDETECT was applied to the event list in the energy range
from 0.5 - 2 keV. Using a detection threshold which ensures less than 1
spurious source per field leads to the detection of 188 sources, while
lowering this threshold to 10 spurious sources per field, allows 262 sources
to be identified in this energy range. This is a significant increase (well
above the number expected if all the additional sources were spurious), thus
the authors retained this list of 262 sources as their final list of sources
in the NGC 752 field, with the caveat that ~ 10 sources among them are likely
spurious. Note that the existence of ~ 10 spurious sources in the list is not
so much of a problem in this context, because cluster members or candidate
members are identified by the existence of a visible or near-IR counterpart.
The authors searched for 2MASS counterparts to the X-ray sources using the
2MASS Point Source Catalogue (PSC) and a search radius of 3 arcsec and found
a counterpart for 43 sources. Searching within the Point Source Reject Table
of the 2MASS Extended Mission leads to the further identification of 1
counterpart (source number 87).
OMC2P3CXO Catalog
The OMC-2 and OMC-3 Chandra X-Ray Point Source Catalog contains the results
of the Chandra X-ray observation of Orion Molecular Clouds 2 and 3 (OMC-2 and
OMC-3). A deep exposure of ~100 ks detects ~400 X-ray sources in the field of
view (FOV) of the ACIS array, providing one of the largest X-ray catalogs in
a star-forming region as of the date that this was published (February 2002).
Coherent studies of the source detection, time variability, and energy
spectra were performed. The authors classified the X-ray sources into Class
I, Class II, and Class III+MS types based on the J-, H-, and K-band colors of
their near-infrared counterparts, and discussed the X-ray properties
(temperature, absorption, and time variability) along these evolutionary
phases.
The results of the X-ray imaging analysis and a correlation with the 2MASS
Catalog are given for all the detected X-ray sources. Notice that the
sources '[TKT2002] I1' - '[TKT2002] I354' and '[TKT2002] S1' -
'[TKT2002] S11' were detected in the total-band image (0.5 - 8.0 keV)
images of the ACIS-I and the ACIS-S2 CCDs, respectively, but that
source '[TKT2002] I355' - '[TKT2002] I369' and '[TKT2002] S12' -
'[TKT2002] S13' were detected only in the hard-band (2.0 - 8.0 keV)
images of the ACIS-I and the ACIS-S2 CCDs, and '[TKT2002] I370' -
'[TKT2002] I385' were detected only in the soft-band (0.5 - 2.0 keV)
image of the ACIS-I. No new source was detected in the soft band image of
the ACIS-S2 CCD.
OMEGCENCX2 Catalog
The authors identify 233 X-ray sources, of which 95 are new, in a 222-ks
exposure of omega Centauri with the Chandra X-ray Observatory's Advanced CCD
Imaging Spectrometer detector. The limiting unabsorbed flux in the core is
fX(0.5-6.0keV) ~= 3 x 10-16 erg/s/cm2 (Lx ~= 1 x 1030 erg/s at
5.2kpc). The authors estimate that ~60 +/- 20 of these are cluster members,
of which ~30 lie within the core (rc = 155 arcsec), and another ~30 between
1-2 core radii. They identify four new optical counterparts, for a total of
45 likely identifications. Probable cluster members include 18 cataclysmic
variables (CVs) and CV candidates, one quiescent low-mass X-ray binary, four
variable stars, and five stars that are either associated with omega Cen's
anomalous red giant branch or are sub-subgiants. The authors estimate that
the cluster contains 40 +/- 10 CVs with L_x_> 1031 erg/s, confirming that
CVs are underabundant in omega Cen relative to the field. Intrinsic
absorption is required to fit X-ray spectra of six of the nine brightest CVs,
suggesting magnetic CVs, or high-inclination systems. Though no radio
millisecond pulsars (MSPs) are currently known in omega Cen, more than 30
unidentified sources have luminosities and X-ray colors like those of MSPs
found in other globular clusters; these could be responsible for the
Fermi-detected gamma-ray emission from the cluster. The authors identify a CH
star as the counterpart to the second brightest X-ray source in the cluster
and argue that it is a symbiotic star. This is the first such giant/white
dwarf binary to be identified in a globular cluster.
The data were obtained over two long exposures of omega Cen using the imaging
array of the Chandra X-ray Observatory's ACIS-I on 2012 April 16 and 17. The
data sets have a combined exposure time of ~222ks (173.7 and 48.5ks for
ObsIDs 13726 and 13727, respectively).
OMEGCENCXO Catalog
The authors analyzed a ~ 70 ks Chandra Advanced CCD Imaging Spectrometer
(ACIS) exposure of the globular cluster Omega Cen (NGC 5139). The ~ 17' x 17'
field of view fully encompasses three cluster core radii and almost twice the
half-mass radius. They detected 180 sources to a limiting flux of ~ 4.3 x10
-16 erg/cm2/s (Lx = 1.2 x 1030 erg/s at the 4.9 kpc distance to the
cluster). After accounting for the number of active galactic nuclei and
possible foreground stars among the detected X-ray sources, they estimate
that 45-70 of the sources are cluster members. Four of the X-ray sources have
previously been identified as accreting compact binaries in the cluster -
three cataclysmic variables (CVs) and one quiescent neutron star. Correlating
the Chandra positions with known variable stars yields 8 matches, of which 5
are probable cluster members that are likely to be binary stars with active
coronae. Extrapolating these optical identifications to the remaining
unidentified X-ray source population, the authors estimate that 20 - 35 of
the sources are CVs and a similar number are active binaries. This likely
represents most of the CVs in the cluster, but only a small fraction of all
the active binaries. The authors place a 2-sigma upper limit of Lx < 3 x
1030 erg/s on the integrated luminosity of any additional faint, unresolved
population of sources in the core of the cluster. In their paper, they
explore the significance of these findings in the context of primordial
versus dynamical channels for CV formation. They note that the number of CVs
per unit mass in Omega Cen is at least 2 - 3 times lower than in the field,
suggesting that primordial binaries that would otherwise lead to CVs are
being destroyed in the cluster environment.
The authors obtained 2 exposures of Omega Cen using the imaging array of the
Advanced CCD Imaging Spectrometer (ACIS-I) on 2000 January 24 - 25, in "very
faint" (VF) mode. The total exposure time was 72.4 ks. The authors determined
source counts using 95% encircled energy radii as determined from model PSFs,
derived using the CIAO tool mkpsf at an intermediate energy of ~ 1.5 keV (the
PSF shape being somewhat energy dependent). Counts were extracted in three
bands: "soft" (0.5 - 1.5 keV), "medium" (0.5 - 4.5 keV), and "hard" (1.5 -
6.0 keV). The authors determined the background to subtract from each source
by dividing the image into 1 arcminute-wide annuli centered on the aim point
in chip 3 (the innermost "annulus" being a circle of radius 1.5 arcminutes).
Background values adopted for sources in a given annulus were averages
determined from several source-free regions within that annulus, after
verifying that the background levels were azimuthally symmetric. For 12
sources ( source_numbers 11b, 12b, 13e, 22c, 32c, 41b, 41c, 84a, 84b, 84c,
93a, and 93b) that fell in the chip gaps or near the outer edge of a chip,
background regions were chosen specifically to reflect these conditions.
Local background determinations were also made for a small number of sources
to the west of the cluster center that lie on or near a large diffuse X-ray
source ~7 arcminutes west of the cluster center (see below). Following
background subtraction, the authors applied aperture corrections and also
corrected for reduced effective exposure times off-axis and in the chip gaps
using the exposure map.
ONCCXOOPT Catalog
In the first of two companion papers on the Orion Nebula Cluster (ONC), the
authors presented their analysis of a 63 ks Chandra HRC-I observation that
yielded 742 X-ray detections within the 30' x 30' field of view. To
facilitate their interpretation of the X-ray image, they compiled a
multi-wavelength catalog of nearly 2900 known objects in the region by
combining 17 different catalogs from the recent literature. They defined two
reference groups: an infrared sample, containing all objects detected in the
K band, and an optical sample comprising low-extinction, well-characterized
ONC members. They showed for both samples that field object contamination is
generally low. Their X-ray sources are primarily low-mass ONC members. The
detection rate for optical sample stars increases monotonically with stellar
mass from zero at the brown dwarf limit to ~100% for the most massive stars
but shows a pronounced dip between 2 and 10 Msun. They determined LX and
LX/Lbol or all stars in their optical sample and utilized this
information in their companion paper to study correlations between X-ray
activity and other stellar parameters.
In particular, the authors assembled an extensive catalog of known
X-ray/optical/IR and radio objects that fell within the HRC FOV. In addition
to their list of HRC sources and the Chandra source lists of Garmire et al.
(2000, CDS Cat. <J/AJ/120/1426>) and Schulz et al. (2001, CDS Cat.
<J/ApJ/549/441>), they considered 14 catalogs from recent publications,
producing a database of nearly 2900 distinct objects reported in at least one
of the studies considered. A full list of references is given in the first
column of Table 2 of the reference paper, along with a concise classification
of the work and the referenced table number(s) from the original work. The
authors' ONC optical sample is comprised of stars in the HRC FOV for which
they have a mass estimate, whose values of the visual absorption AV are
less than 3.0, and which are either confirmed proper motion members or have
unknown proper motion (see Section 3.4.1 of the reference paper). For the 696
stars of this optical sample, this HEASARC table (the full version of Table 4
of the reference paper) lists sky position, mass, age, rotational period, Ca
II line equivalent width, HRC basal count rate (see Section 5 of the
reference paper), X-ray luminosity, and LX/Lbol (see Sections 4 and 5 of
the reference paper).
ONCCXOXRAY Catalog
In the first of two companion papers on the Orion Nebula Cluster (ONC), the
authors presented their analysis of a 63 ks Chandra HRC-I observation that
yielded 742 X-ray detections within the 30' x 30' field of view. To
facilitate their interpretation of the X-ray image, they compiled a
multi-wavelength catalog of nearly 2900 known objects in the region by
combining 17 different catalogs from the recent literature. They defined two
reference groups: an infrared sample, containing all objects detected in the
K band, and an optical sample comprising low-extinction, well-characterized
ONC members. They showed for both samples that field object contamination is
generally low. Their X-ray sources are primarily low-mass ONC members. The
detection rate for optical sample stars increases monotonically with stellar
mass from zero at the brown dwarf limit to ~100% for the most massive stars
but shows a pronounced dip between 2 and 10 Msun. They determined LX and
LX/Lbol or all stars in their optical sample and utilized this
information in their companion paper to study correlations between X-ray
activity and other stellar parameters.
In particular, the authors assembled an extensive catalog of known
X-ray/optical/IR and radio objects that fell within the HRC FOV. In addition
to their list of HRC sources and the Chandra source lists of Garmire et al.
(2000, CDS Cat. <J/AJ/120/1426>) and Schulz et al. (2001, CDS Cat.
<J/ApJ/549/441>), they considered 14 catalogs from recent publications,
producing a database of nearly 2900 distinct objects reported in at least one
of the studies considered. A full list of references is given in the first
column of Table 2 of the reference paper, along with a concise classification
of the work and the referenced table number(s) from the original work.
The HRC on board the Chandra X-Ray Observatory (Weisskopf et al.,
2002PASP..114....1W) observed the ONC for 63.2ks on 2000 February 4.
The pointing (R.A. = 5h 35m 17s, DE=-5{deg} 23' 16" (J2000.0)) was
chosen to place the Trapezium region and the bright O star Theta1
Ori C in the center of the field of view (FOV). A good fraction of the
ONC region was included in the 30' x 30' HRC FOV. This HEASARC table
lists the properties of the 742 X-ray sources detected in this observation
as presented in the full version of Table 1 of the reference paper.
ORIONFFCXO Catalog
This table contains the results of Chandra observations of two
flanking fields (FFs) in Orion outside the Orion Nebula Cluster (ONC), in the
form of a catalog of 417 sources, which includes X-ray luminosity, optical and
infrared photometry, and X-ray variability information. 91 variable sources
were found, 33 of which have flarelike light curves, and 11 of which have
a pattern of a steady increase or decrease over a 10 hour period. The optical
and infrared photometry for the stars identified as X-ray sources are
consistent with most of these objects being pre-main-sequence stars with ages
younger than 10 Myr.
The two flanking fields in Orion were observed with the Advanced CCD Imaging
Spectrometer (ACIS) detector on board the Chandra X-Ray Observatory. The
north Orion flanking field (NOFF) is centered at a J2000 RA and Declination
of 05:35:19, -04:48:15, which is about 36' (~5 pc, at a distance of 470 pc)
north of the Trapezium cluster and was observed on 2002 August 26 with
a total exposure time of 48.8 ks. The south Orion flanking field (SOFF),
centered at a J2000 RA and Declination of 05:35:06, -05:40:48, which is
about 17' (~ 2.5pc, at a distance of 470 pc) south of the Trapezium cluster,
was observed on 2002 September 6 with a total exposure time of 47.9 ks.
The data analysis for these observations was performed in the same manner
as described in Ramirez et al. (2004, AJ, 127, 2659) for a similar
observation of a field in NGC 2264, which should be consulted for the full
details. (See also the help file for the HEASARC version of the catalog
from the latter reference available at /W3Browse/chandra/ngc2264cxo.html ).
RCW108CXO Catalog
This table contains some of the results of an approximately 90 ks Chandra
observation of a complex region that hosts multiple sites of recent and
active star formation in ARA OB1a. The field is centered on the embedded
cluster RCW 108-IR and includes a large portion of the open cluster NGC 6193.
The authors detected over 420 X-ray sources in the field and combined these
data with deep near-IR, Spitzer/IRAC and Midcourse Space Experiment (MSX)
mid-IR data. They find that about 360 of the X-ray sources have near-IR
counterparts. They divide the region into five parts based on the X-ray point
source characteristics and extended 8 micron emission. The most clearly
defined regions are the central region, identified by embedded sources with
high luminosities in the both the near-IR and X-ray as well as high X-ray
temperatures (~3 keV), and the eastern region, identified by low extinction
and ~1 keV X-ray temperatures. Other regions, identified by their directional
relationship to RCW 108-IR, are less uniform, representing combinations of
the first two regions, independent star formation epochs, or both. The
cluster members range in X-ray luminosity from 1029 to 1033 erg s-1.
Over 18% of the cluster members with over 100 counts exhibit flares. All
sources with over 350 counts are variable. Overall about 10% (16% in RCW
108-IR) appear to have optically thick disks as derived from their position
in the (J - H), (H - K) diagram. The disk fraction becomes much higher when
IRAC data are employed. The largest fraction of X-ray sources is best
described as possessing some disk material via a more detailed extinction
fitting. The authors fit the bulk of the X-ray spectra as absorbed
Raymond-Smith-type plasmas, and find that the column to the RCW 108-IR
members varies from 1021 to 1023 cm-2. They find that the field
contains 41 candidate O or B stars, and estimate that the total number of
pre-main-sequence stars in the field is about 1600 +/- 200. Approximately 800
are confined to the 3' (~1.1 pc) central region.
The field was observed by Chandra on 2004 October 25 starting at 02:37 UT for
92.2 ks of total time and 88.8 ks of so-called "good-time" (ObsId 4503). The
ACIS was used in the nominal imaging array (chips I0-I3) which provides a
field of view of approximately 17' by 17' (~6.5 pc on a side). The aimpoint
was at RA, Dec = 16:39:58.7, -48:51:54.4 (J2000.0). In addition, the S2 and S3
chips were on and located over IRAS 16379-4856. About 20 point sources were
detected associated with this object; however, the analysis of these data is
not presented here because they are far off-axis.
RCW38CXO Catalog
This table contains the results of a 96.7-ks Chandra observation of one of
the youngest, most embedded, and most massive young stellar clusters studied
to this date in X-rays, namely the embedded young cluster, RCW 38. 460 X-ray
sources were detected in the field, of which 360 are confirmed to be
associated with the RCW 38 cluster. The cluster members range in luminosity
from 1030 to 1033.5 erg/s. Over 10% of the cluster members with over 100
counts were found to exhibit flares, while about 15% of the cluster members
with over 30 counts were variable. Of the sources identified as cluster
members, 160 have near-infrared (NIR) counterparts either in the Two Micron
All Sky Survey (2MASS) database or which were detected via Very Large
Telescope observations. Of these, about 20% appear to have optically thick
disks. An additional 353 cluster members were identified through NIR
observations, of which at least 50% possess optically thick disks. Over 100
X-ray sources were fit as absorbed Raymond-Smith-type plasmas and the authors
found that the column to the cluster members varies from 1021.5 to 1023
cm-2. Comparing the gas to dust absorption signatures in these stars they
found NH = AV (2 x 1021) cm-2. They also found that the cluster
contains 31 candidate OB stars and is centered about 10" (0.1 pc) west of the
primary source of its ionization, the O5 star IRS 2. The cluster has a peak
central density of about 400 X-ray sources pc-2. The authors estimate that
the total cluster membership exceeds 2000 stars.
The Chandra observation of RCW 38 took place on 2001 December 10-11 and
lasted 96.7 ks. It used Advanced CCD Imaging Spectrometer (ACIS) chips 0, 1,
2, 3, 6 and 7 in very faint mode. The combined field of view (FOV) of the 4
chips in the imaging array (0-3, ACIS-I) is 16.9' x 16.9'. The aimpoint of
the array was 8 59 19.20, -47 30 22.0 (J2000.0), and Chandra's roll angle was
51 degrees. The source detection algorithm PWDetect was run on the cleaned
events list across the entire ACIS-I array, and found 460 sources, including
31 sources with more than 200 net counts, 49 sources with 100-200 net counts,
71 sources with 50-100 net counts, and 78 sources with 20-50 net counts. NIR
matches were found for 349 of the 460 X-ray sources, including 294 of the 360
cluster members and 55 of the 100 nonmembers.
RCW38CXO2 Catalog
This table contains some of the results from a study of the structure of the
high-mass star-forming region RCW 38 and the spatial distribution of its
young stellar population. Spitzer Infrared Array Camera (IRAC) photometry
(3-8 micron) is combined with Two Micron All Sky Survey (2MASS) near-IR data
to identify young stellar objects (YSOs) by IR-excess emission from their
circumstellar material. Chandra X-ray data are used to identify class III
pre-main-sequence stars lacking circumstellar material. The authors identify
624 YSOs: 23 class 0/I and 90 flat spectrum (FS) protostars, 437 class II
stars, and 74 class III stars. They also identify 29 (27 new) O star
candidates over the IRAC field. Seventy-two stars exhibit IR-variability,
including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative
candidates are identified by their location in the IRAC [3.6] versus
[3.6]-[5.8] color-magnitude diagram. The authors find strong evidence of
subclustering in the region. Three subclusters were identified surrounding
the central cluster, with massive and variable stars in each subcluster. The
central region shows evidence of distinct spatial distributions of the
protostars and pre-main-sequence stars. A previously detected IR cluster,
DB2001_Obj36, has been established as a subcluster of RCW 38. This suggests
that star formation in RCW 38 occurs over a more extended area than
previously thought. The gas-to-dust ratio is examined using the X-ray derived
hydrogen column density, NH and the K-band extinction, and found to be
consistent with the diffuse interstellar medium, in contrast with Serpens and
NGC 1333. The authors posit that the high photoionizing flux of massive stars
in RCW 38 affects the agglomeration of the dust grains.
This table contains the list of 536 X-ray sources found in the Chandra data
using a three-pass method with the CIAO 3.4 Wavdetect tool.
RCW49CXO Catalog
This table contains the list of X-ray sources detected in a high-resolution
X-ray imaging study of the stellar population in the Galactic massive
star-forming region RCW 49 and its central OB association Westerlund 2. The
authors obtained a ~ 40 ks X-ray image of a ~ 17' x 17' field using the
Chandra X-Ray Observatory and deep NIR images using the Infrared Survey
Facility in a concentric ~ 8.3' x 8.3' region. They detected 468 X-ray
sources with a photometric significance >=1.0 and a 1% or less chance of
being a background fluctuation, and identified optical, near-infrared (NIR),
and Spitzer mid-infrared (MIR) counterparts for 379 of them. The
unprecedented spatial resolution and sensitivity of the X-ray image, enhanced
by optical and infrared imaging data, yielded the following results:
(1) The central OB association Westerlund 2 is resolved for the first time in
the X-ray band. X-ray emission is detected from all spectroscopically
identified early-type stars in this region.
(2) Most (~ 86%) X-ray sources with optical or infrared identifications are
cluster members in comparison with a control field in the Galactic plane.
(3) A loose constraint (2-5 kpc) for the distance to RCW 49 is derived from
the mean X-ray luminosity of T Tauri stars.
(4) The cluster X-ray population consists of low-mass pre-main-sequence and
early-type stars as obtained from X-ray and NIR photometry. About 30 new OB
star candidates are identified.
(5) The authors estimate a cluster radius of 6' - 7' based on the X-ray
surface number density profiles.
(6) A large fraction (~ 90%) of cluster members are identified individually
using complimentary X-ray and MIR excess emission.
(7) The brightest five X-ray sources, two Wolf-Rayet stars and three O stars,
have hard thermal spectra.
The X-ray observation of RCW 49 was carried out using the Advanced CCD Imaging
Spectrometer (ACIS) on board the Chandra X-Ray Observatory from 2003 August 23
UT 18:20 to August 24 UT 4:54. Four imaging array (ACIS-I) chips covered a
17 by 17 arcminutes field centered at (R.A., Dec.) = (10h24m00.5s, -57d 45'
18") in the equinox J2000.0 for a 36.7 ks exposure. ACIS-I covers the 0.5 -
8.0 keV energy band with a spectral resolution of ~ 150 eV at 6 keV and a
point-spread function (PSF) radius of ~ 0.5" within ~ 2' of the
on-axis position, degrading to ~ 6" at a 10' off-axis angle. The data were
taken with the very faint telemetry mode and the timed exposure CCD operation
with a frame time of 3.2 s.
Sources with photometric significance of larger than 2 were fitted with an
absorbed thin thermal plasma model. The abundance was fixed to be 0.3 times the
solar value. Fits lacking uncertainties, fits with large uncertainties, and
fits with frozen parameters should be viewed merely as splines to the data to
obtain rough estimates of the X-ray luminosities: the listed parameter values
are considered unreliable in such cases.
The authors also conducted NIR observations on 2004 December 25 and 28 using
the Simultaneous three-color Infrared Imager for Unbiased Surveys (SIRIUS)
mounted on the Cassegrain focus of the IRSF 1.4 m telescope at the South
African Astronomical Observatory. SIRIUS is a NIR imager capable of obtaining
simultaneous images in the J, H, and Ks bands. The instrument is equipped
with three HAWAII arrays of 1024 by 1024 pixels. The pixel scale of 0.45"
is an excellent match with the on-axis spatial resolution of Chandra. The
authors covered 8.3 by 8.3 arcminute fields at two positions, one aimed at
RCW 49 (10h24m01.9s, -57d 45' 31") and the other at a control region.
RHOOPHCXO Catalog
This catalog of X-ray sources represents some of the results of a systematic
study of X-ray flares from low-mass young stellar objects, using two deep
exposure Chandra observations of the main region of the rho Ophiuchi
star-forming cloud. From 195 X-ray sources, including class I-III pre-main
sequence sources and some young brown dwarfs, a total of 71 X-ray flares were
detected.
The Chandra X-ray Observatory (Weisskopf et al., 2002PASP..114....1W)
observed the central region of rho Oph twice with a deep exposure of the
ACIS-I array, consisting of four abutted X-ray CCDs. The first observation
(here and after, obs. BF) covered the south-east 17.4' x 17.4' area,
including cores B, C, E, and F, while the second observation (obs. A) covered
the north-west area centered on core A (Loren et al., 1990ApJ...365..269L).
This table contains data and the results of spectral and timing analyses on
the 195 sources detected in the two rho Oph fields, 9 of which were detected
in both fields and are therefore listed twice (A-61=BF-2, A-64=BF-4,
A-65=BF-5, A-69=BF-7, A-75=BF-11, A-77=BF-15, A-78=BF-16, A-79=BF-17, and
A-81 = BF-19). Sources which flared have multiple entries, with one entry
(typically, but not always) listing the properties of the quiescent emission,
and additional entries for individual flares which were analyzed separately.
For the very faint sources for which the temperatures obtained from X-ray
spectral analyses were not constrained, there are typically two entries in
this table per source, one of which gives the results of a spectral analysis
in which the temperature was fixed at 1 keV (11.6 MK) and the other in which
the temperature was instead fixed at 5 keV (58 MK). Thus, there are more
entries (306) in this HEASARC table than the number (195) of detected rho Oph
X-ray sources.
ROS13HRCXO Catalog
This table contains some of the results from a Chandra ACIS-I survey of a
high-latitude region at RA, Dec = 13 hours, +38 degrees which was earlier
observed with ROSAT and which had recently been observed by XMM-Newton for
200 ks. XMM-Newton was expected to provide good-quality X-ray spectra for
over 200 sources with fluxes around the knee of the log N /log S
distribution, which are responsible for the bulk of the X-ray background. The
main aim of the Chandra observations was to provide arcsecond, or better,
positions, and hence reliable identifications, for the XMM-Newton sources.
The ACIS-I observations were arranged in a mosaic of four 30-ks pointings,
covering almost all of the 15-arcminute radius XMM-Newton/ROSAT field. 214
Chandra sources were detected above a Cash likelihood statistic of 25, which
approximates to a 5-sigma significance, to a limiting flux of ~ 1.3 x
10-15erg/cm2/s (0.5 - 7 keV). Optical counterparts were derived from a
Subaru SuprimeCam image reaching to R ~ 27. The very large majority of the
Chandra sources have an optical counterpart, with the distribution peaking at
23 < R < 24, although 14 have no counterpart to R = 27. The fraction of X-ray
sources with no identification brighter than R = 27 is similar to that found
in deeper Chandra surveys.
The majority of the identifications are with galaxies. As found in other
Chandra surveys, there is a very wide range of optical magnitudes for a given
X-ray flux, implying a range of emission mechanisms, and many sources have
high LX/Lopt ratios, implying absorption at moderate redshift. Comparison
with the earlier ROSAT survey shows that the accuracy of the ROSAT positions
agrees very well with the predictions from simulations by McHardy et al. and
that the large majority of the identifications were correct.
ROSETTECXO Catalog
The authors of this study have explored the young stellar populations in the
Rosette Molecular Cloud (RMC) region with high spatial resolution X-ray
images from the Chandra X-ray Observatory, which are effective in locating
weak-lined T Tauri stars as well as disk-bearing young stars. A total of 395
X-ray point sources are detected, 299 of which (76%) have an optical or
near-infrared (NIR) counterpart identified from deep FLAMINGOS images. From
X-ray and mass sensitivity limits, the authors infer a total population of
~1700 young stars in the survey region. Based on smoothed stellar surface
density maps, they investigate the spatial distribution of the X-ray sources
and define three distinctive structures and substructures within them.
Structures B and C are associated with previously known embedded IR clusters,
while structure A is a new X-ray-identified unobscured cluster. A high-mass
protostar RMCX 89 = IRAS 06306+0437 and its associated sparse cluster are
studied. The different subregions are not coeval but do not show a simple
spatial-age pattern. Disk fractions vary between subregions and are generally
<~ 20% of the total stellar population inferred from the X-ray survey. The
data are consistent with speculations that triggered star formation around
the H II region is present in the RMC, but do not support a simple sequential
triggering process through the cloud interior. While a significant fraction
of young stars are located in a distributed population throughout the RMC
region, it is not clear if they originated in clustered environments.
This HEASARC table contains the 348 primary sources listed in Table 1 of the
reference paper, as well as the 47 tentative sources listed in Table 2 (the
latter having a likelihood > 10-3 of being a spurious background
fluctuation based on Poisson statistics), to make a total of 395 X-ray
sources. The information on optical and infrared counterparts to these X-ray
sources which was provided in Table 4 of the reference paper has also been
included herein. In order to allow users to clearly identify these 2 samples,
the HEASARC has created a parameter source_sample which is set to 'P' for the
Table 1 primary sources and to 'T' for the Table 2 tentative sources. This
HEASARC table also contains the X-ray spectroscopic information derived for
158 sources which have photometric significance (the snr parameter) >= 2.0
which was presented in Table 3 of the reference paper. All spectral fits used
the "wabs(apec)" model in XSPEC and assumed 0.3 * Z_Sun abundances. The
quoted emission measures and X-ray luminosities assume a distance to the
Rosette molecular cloud of 1.4 kpc.
S254258CXO Catalog
The aim of this study was to find an explanation for the
remarkable morphology of the central part of the S254-S258 star forming
complex. The authors performed a deep Chandra X-ray observation of the
S254-S258 region in order to efficiently discriminate young stars (with and
without circumstellar matter) from the numerous older field stars in the area.
They detected 364 X-ray point sources in a 17' x 17' (~ 8 x 8 pc) field. This
X-ray catalog provides, for the first time, a complete sample of all young
stars in the region down to about 0.5 M_{sun}_. A clustering analysis
identifies three significant clusters: the central embedded cluster S255-IR
and two smaller clusterings in S256 and S258. Sixty-four X-ray sources can be
classified as members in one of these clusters. After accounting for X-ray
background contaminants, this implies that about 250 X-ray sources constitute
a widely scattered population of young stars, distributed over the full
field-of-view of the X-ray image. This distributed young stellar population is
considerably larger than the previously known number of non-clustered young
stars selected by infrared excesses. Comparison of the X-ray luminosity
function with that of the Orion Nebula Cluster suggests a total population of
~ 2000 young stars in the observed part of the S254-S258 region.
The S254-S258 complex was observed (PI: Preibisch) in November 2009 with the
Imaging Array of the Chandra Advanced CCD Imaging Spectrometer (ACIS-I).
ACIS-I provides a field of view of 17' x 17' on the sky. At the 1.6 kpc
distance of S254-S258 this corresponds to 7.9 x 7.9 pc. The aimpoint of the
observation was RA(J2000) = 06h12m54.0s, Dec(J2000) = +17d 59' 24". The
observation was performed in the standard 'Timed Event, Faint' mode (with
3 x 3 pixel event islands). The total net exposure time of 74725 s (20.76 h)
was split into two parts, separated by about 4 days. The details of these two
observation parts are given in Table 1 of the reference paper.
The authors first employed the wavdetect algorithm (Freeman et al. 2002, ApJS,
138, 185, a CIAO mexican-hat wavelet source detection tool) for locating X-ray
sources in the merged image, and used a rather low detection threshold of
10-5. This step was performed in three different energy bands, the total
band (0.5 - 8.0 keV), the soft band (0.5 - 2.0 keV), and the hard band
(2.0 - 8.0) keV, and with wavelet scales between 1 and 16 pixels. They also
performed a visual inspection of the images and added some 30 additional
candidates to the merged catalog from the wavelet analysis, resulting in a
final catalog of 511 potential X-ray sources. To clean this catalog from
spurious sources, they then performed a detailed analysis of each individual
candidate source with the ACIS Extract (AE hereafter) software package
(Broos et al. 2010, ApJ, 714, 1582).
The Poisson probability (PB) associated with the "null hypothesis", i.e.
that no source exists and the extracted events are solely due to Poisson
fluctuations in the local background, was computed for each source using AE.
All candidate sources with PB > 0.01 were rejected as background
fluctuations. After 8 iterations of this pruning procedure the final catalog
consisted of 364 sources. It contains 344 primary sources with PB < 0.003,
and 20 tentative sources with 0.003 < PB < 0.01.
To obtain an estimate of the intrinsic, i.e. extinction-corrected, X-ray
luminosity for sources that are too weak for a detailed spectral analysis, the
authors used the XPHOT software, developed by Getman et al. (2010, ApJ, 708,
1760). XPHOT is based on a non-parametric method for the calculation of fluxes
and absorbing X-ray column densities of weak X-ray sources. X-ray extinction
and intrinsic flux are estimated from the comparison of the apparent median
energy of the source photons and apparent source flux with those of high
signal-to-noise spectra that were simulated using spectral models
characteristic of much brighter sources of similar class previously studied in
detail. This method requires at least 4 net counts per source (in order to
determine a meaningful value for the median energy) and can thus be applied to
255 of the 364 sources in this table. To calculate luminosities, a distance
of 1.6 kpc was assumed. The resulting intrinsic X-ray lumonosities range
from 1029.4 to 1032.3 erg s-1.
SDSSCXOQSO Catalog
The authors have studied the spectral energy distributions and
evolution of a large sample of optically selected quasars from the Sloan
Digital Sky Survey (SDSS) that were observed in 323 Chandra images analyzed
by the Chandra Multiwavelength Project (ChaMP). Their highest-confidence
matched sample (which this HEASARC table comprises) includes 1135 X-ray
detected quasars in the redshift range 0.2 < z < 5.4, representing some 36
Msec of effective exposure. In their paper, the authors provide catalogs of
QSO properties, and describe their novel method of calculating X-ray flux
upper limits and effective sky coverage. Spectroscopic redshifts are available
for about 1/3 of the detected sample; elsewhere, redshifts are estimated
photometrically. The authors have detected 56 QSOs with redshift z > 3,
substantially expanding the known sample. They find no evidence for evolution
out to z ~ 5 for either the X-ray photon index Gamma or for the ratio of
optical/UV to X-ray flux Alpha_ox. About 10% of detected QSOs show best-fit
intrinsic absorbing columns greater than 1022 cm-2, but the fraction might
reach ~1/3 if most nondetections are absorbed. The authors confirm a
significant correlation between Alpha_ox and optical luminosity, but it
flattens or disappears for fainter (M_B >~ -23) active galactic nucleus (AGN)
alone. They report significant hardening of Gamma both toward higher X-ray
luminosity, and for relatively X-ray loud quasars. These trends may represent
a relative increase in nonthermal X-ray emission, and their findings thereby
strengthen analogies between Galactic black hole binaries and AGN. For
uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption
line QSOs, they find no evidence for unusual distributions of either
Alpha_ox or Gamma.
Much more information on the SDSS is available at the project's web site
at http://www.sdss.org/.
SDSSS82CXO Catalog
This table contains some of the data from the latest release of the Stripe 82
X-ray (82X) survey point-source catalog, which currently covers 31.3 deg2
of the Sloan Digital Sky Survey (SDSS) Stripe 82 Legacy field. In total,
6,181 unique X-ray sources are significantly detected with XMM-Newton (> 5
sigma) and Chandra (> 4.5 sigma). This 31 deg2 catalog release includes
data from XMM-Newton cycle AO 13, which approximately doubled the Stripe 82X
survey area. The flux limits of the Stripe 82X survey are 8.7 x 10-16 erg
s-1 cm-2, 4.7 x 10-15 erg s-1 cm-2, and 2.1 x 10-15 erg s-1
cm^=2^ in the soft (0.5 - 2.0 keV), hard (2 - 10 keV), and full (0.5 - 10
keV) bands, respectively, with approximate half-area survey flux limits of
5.4 x 10-15 erg s-1 cm-2, 2.9 x 10-14 erg s-1 cm-2, and 1.7 x
10-14 erg s-1 cm-2, respectively. The authors matched the X-ray source
lists to available multi-wavelength catalogs, including updated matches to
the previous release of the Stripe 82X survey; 88% of the sample is matched
to a multi-wavelength counterpart. Due to the wide area of Stripe 82X and
rich ancillary multi-wavelength data, including coadded SDSS photometry,
mid-infrared WISE coverage, near-infrared coverage from UKIDSS and VISTA
Hemisphere Survey (VHS), ultraviolet coverage from GALEX, radio coverage from
FIRST, and far-infrared coverage from Herschel, as well as existing ~30%
optical spectroscopic completeness, this study is beginning to uncover rare
objects, such as obscured high-luminosity active galactic nuclei at high
redshift. The Stripe 82X point source catalog is a valuable data set for
constraining how this population grows and evolves, as well as for studying
how they interact with the galaxies in which they live. The authors derive
the XMM-Newton number counts distribution and compare it with their
previously reported Chandra log N - log S relations and other X-ray surveys.
Throughout this study, the authors adopt a cosmology of H0 = 70 km s-1
Mpc-1, OmegaM = 0.27, and Lambda = 0.73.
The XMM-Newton and Chandra X-ray sources were matched with sources in the
SDSS, WISE, UKIDSS, VHS, GALEX, FIRST and Herschel databases using the
maximum likelihood estimator (MLE) method, as discussed in detail in Section
4 of the reference paper. This table contains the list of 1,146 Chandra
sources detected in the SDSS Stripe 82. A related table SDSSS82XMM contains
the list of 5,220 XMM-Newton sources detected in the SDSS Stripe 82.
SELHCGCXO Catalog
This table contains the Chandra X-ray point source catalogs for 9 Hickson
Compact Groups (HCGs, 37 galaxies) at distances of 34 to 89 Mpc. The authors
perform detailed X-ray point source detection and photometry and interpret
the point source population by means of simulated hardness ratios. They thus
estimate X-ray luminosities (LX) for all sources, most of which are too
weak for reliable spectral fitting. For all sources, they provide counts,
count rates, power-law indices (Gamma), hardness ratios, and LX, in the
full (0.5-8.0 keV), soft (0.5-2.0 keV) and hard (2-8 keV) bands. In their
paper, the authors use optical emission-line ratios from the literature to
re-classify 24 galaxies as star-forming, accreting onto a supermassive black
hole (AGNs), transition objects, or low-ionization nuclear emission regions.
Two-thirds of their galaxies have nuclear X-ray sources with Swift/UVOT
counterparts. Two nuclei have full-band X-ray luminosities >= 1042 erg
s-1, are strong multi-wavelength AGNs, and follow the known alphaOX - nu
L_nu(near-UV)_ correlation for strong AGNs. Otherwise, most nuclei are X-ray
faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary
population, and fall into the 'non-AGN' locus in alphaOX - nu
L_nu(near-UV)_ space, which also hosts other normal galaxies.
Each group was observed at the aim point of the back-illuminated S3 CCD of
Chandra's Advanced CCD Imaging Spectrometer (ACIS), with the exception of HCG
90, which was observed with the ACIS-I array. The details of the 9 Chandra
observations analyzed herein are given in Table 1 of the reference paper. The
full details of the X-ray analysis and point source detection procedures are
given in Section 3 of the reference paper.
SFGALHMXB Catalog
Based on a homogeneous set of X-ray, infrared and ultraviolet observations
from Chandra, Spitzer, GALEX and 2MASS archives, the authors studied
populations of high-mass X-ray binaries (HMXBs) in a sample of 29 nearby
star-forming galaxies and their relation with the star formation rate (SFR).
In agreement with previous results, the authors find that HMXBs are a good
tracer of the recent star formation activity in the host galaxy and their
collective luminosity and number scale with the SFR, in particular, LX ~
2.6 x 1039 x SFR. However, the scaling relations still bear a rather large
dispersion of rms ~ 0.4 dex, which the authors believe is of a physical
origin.
This table contains the catalog of 1055 compact X-ray sources detected within
the D25 ellipse for galaxies of this sample which the authors used to
construct the average X-ray luminosity function (XLF) of HMXBs with
substantially improved statistical accuracy and better control of systematic
effects than achieved in previous studies. The XLF follows a power law with
slope of 1.6 in the log(LX) ~ 35 - 40 luminosity range with a moderately
significant evidence for a break or cut-off at LX ~ 1040 erg/s. As
before, the authors did not find any features at the Eddington limit for a
neutron star or a stellar mass black hole.
In their paper, the authors discuss the implications of their results for the
theory of binary evolution. In particular, they estimate the fraction of
compact objects that once during their lifetime experienced an X-ray active
phase powered by accretion from a high mass companion and obtain a rather
large number, fX ~ 0.2 x (0.1 Myr/taux), where taux is the life time of
the X-ray active phase. This is about 4 orders of magnitude more frequent
than in low-mass X-ray binaries (LMXBs). The authors also derive constrains
on the mass distribution of the secondary star in HMXBs.
Note that, in their paper, the authors estimate that ~ 300 of the 1055
sources are likely to be background AGNs (cosmic X-ray background or CXB
sources) and that the majority (<~ 700) of the remaining ~ 750 sources are
young HMXB systems associated with star formation in their host galaxies.
SFINCSPCM Catalog
The Star Formation in Nearby Clouds (SFiNCs) project is aimed at providing a
detailed study of the young stellar populations and of star cluster formation
in the nearby 22 star-forming regions (SFRs) for comparison with the authors'
earlier MYStIX survey of richer, more distant clusters. As a foundation for
the SFiNCs science studies, in the reference paper homogeneous data analyses
of the Chandra X-ray and Spitzer mid-infrared (MIR) archival SFiNCs data are
described, and the resulting catalogs of over 15,300 X-ray and over 1,630,000
mid-infrared point sources are presented. On the basis of their
X-ray/infrared properties and spatial distributions, nearly 8500 point
sources have been identified as probable young stellar members of the SFiNCs
regions. Compared to the existing X-ray/mid-infrared publications, the SFiNCs
member list increases the census of YSO members by 6%-200% for individual
SFRs and by 40% for the merged sample of all 22 SFiNCs SFRs.
Sixty-five X-ray observations of the 22 SFiNCs SFRs made with the imaging
array on the Advanced CCD Imaging Spectrometer (ACIS) were extracted from the
Chandra archive (spanning from 2000 January to 2015 April). See Tables 1 and
2 of the reference paper for the list of SFRs and the log of Chandra ACIS
observations, respectively. The final Chandra-ACIS catalog for the 22 SFiNCs
SFRs comprises 15,364 X-ray sources (presented in Tables 3 and 4 and section
3.2 of the reference paper, and available as the HEASARC table, SFINCSXRAY).
To obtain MIR photometry for X-ray objects and to identify and measure MIR
photometry for additional non-Chandra disky stars that were missed in
previous studies of the SFiNCs regions (typically faint YSOs), the authors
have reduced the archived Spitzer-IRAC data by homogeneously applying the
MYStIX-based Spitzer-IRAC data reduction methods of Kuhn et al. (2013, ApJS,
209, 29) to the 423 Astronomical Object Request (AORs) data sets for the 22
SFiNCs SFRs (listed in Table 5 of the reference paper). As in MYStIX, the
SFiNCs IRAC source catalog retains all point sources with the photometric
signal-to-noise ratio > 5 in both [3.6] and [4.5] um channels. This catalog
covers the 22 SFiNCs SFRs and their vicinities on the sky and comprises
1,638,654 IRAC sources with available photometric measurements for 100%,
100%, 29%, and 23% of these sources in the 3.6, 4.5, 5.8, and 8.0um bands,
respectively (see table 6 and section 3.4 of the reference paper).
Source position cross-correlations between the SFiNCs Chandra X-ray source
catalog and an IR catalog, either the "cut-out" IRAC or 2MASS, were made
using the steps described in section 3.5 of the reference paper.
Using the ensemble of X-ray and infrared data that they have obtained, the
authors selected probable YSOs in the 22 SFRs using selection criteria
described in section 4.1 of the reference paper. Tables 7 and 8 of the
reference paper provide the list of 8,492 SFiNCs probable cluster members
(SPCMs: but see below for a caveat on this number) and their main IR and
X-ray properties (see section 4 of the reference paper). This present HEASARC
table comprises the contents of these two tables. A fuller list of the X-ray
properties of the X-ray-detected SPCMs is available in the HEASARC's
SFINCSXRAY table (q.v.).
SFINCSXRAY Catalog
The Star Formation in Nearby Clouds (SFiNCs) project is aimed at providing a
detailed study of the young stellar populations and of star cluster formation
in the nearby 22 star-forming regions (SFRs) for comparison with our earlier
MYStIX survey of richer, more distant clusters. As a foundation for the
SFiNCs science studies, in the reference paper homogeneous data analyses of
the Chandra X-ray and Spitzer mid-infrared archival SFiNCs data are
described, and the resulting catalogs of over 15,300 X-ray and over 1,630,000
mid-infrared point sources are presented. On the basis of their
X-ray/infrared properties and spatial distributions, nearly 8500 point
sources have been identified as probable young stellar members of the SFiNCs
regions. Compared to the existing X-ray/mid-infrared publications, the SFiNCs
member list increases the census of YSO members by 6%-200% for individual
SFRs and by 40% for the merged sample of all 22 SFiNCs SFRs.
Sixty-five X-ray observations of the 22 SFiNCs SFRs made with the imaging
array on the Advanced CCD Imaging Spectrometer (ACIS) were extracted from the
Chandra archive (spanning from 2000 January to 2015 April). See Tables 1 and
2 of the reference paper for the list of SFRs and the log of Chandra ACIS
observations, respectively. The final Chandra-ACIS catalog for the 22 SFiNCs
SFRs comprises 15,364 X-ray sources (presented in Tables 3 and 4 and section
3.2 of the reference paper, and the contents of this HEASARC table,
SFINCSXRAY).
To obtain MIR photometry for X-ray objects and to identify and measure MIR
photometry for additional non-Chandra disky stars that were missed in
previous studies of the SFiNCs regions (typically faint YSOs), the authors
have reduced the archived Spitzer-IRAC data by homogeneously applying the
MYStIX-based Spitzer-IRAC data reduction methods of Kuhn et al. (2013, ApJS,
209, 29) to the 423 Astronomical Object Request (AORs) data sets for the 22
SFiNCs SFRs (Table 5 of the reference paper). As in MYStIX, the SFiNCs IRAC
source catalog retains all point sources with the photometric signal-to-noise
ratio > 5 in both [3.6] and [4.5] um channels. This catalog covers the 22
SFiNCs SFRs and their vicinities on the sky and comprises 1,638,654 IRAC
sources with available photometric measurements for 100%, 100%, 29%, and 23%
of these sources in the 3.6, 4.5, 5.8, and 8.0um bands, respectively (see
table 6 and section 3.4 of the reference paper).
Source position cross-correlations between the SFiNCs Chandra X-ray source
catalog and an IR catalog, either the "cut-out" IRAC or 2MASS, were made
using the steps described in section 3.5 of the reference paper.
Tables 7 and 8 of the reference paper provide the list of 8,492 SFiNCs
probable cluster members (SPCMs) and their main IR and X-ray properties (see
section 4 of the reference paper): this list as available at the HEASARC as
the SFINCSPCM table (q.v.).
SMCDFSCXO Catalog
This table contains the results of a pair of 100 ks Chandra observations of
the Small Magellanic Cloud (SMC) to survey high-mass X-ray binaries (HMXBs),
stars, and low-mass X-ray binaries (LMXBs)/cataclysmic variables down to LX
= 4.3 x 1032 erg s-1. The two SMC Deep Fields (DFs) are located in the
most active star-forming region of the SMC bar, with Deep Field-1 positioned
at the most pulsar-rich location identified from previous surveys. Two new
pulsars were discovered in outburst, CXOU J004929.7-731058 (P = 892 s) and
CXOU J005252.2-721715 (P = 326 s), and three new HMXB candidates were
identified. Of the 15 Be-pulsars now known in the field, 13 were detected,
with pulsations seen in 9 of them. Ephemerides demonstrate that 6 of the 10
pulsars known to exhibit regular outbursts were seen outside their periastron
phase, and quiescent X-ray emission at LX = 10(33-34) erg s-1 is shown
to be common. Comparison with ROSAT, ASCA, and XMM-Newton catalogs resulted
in positive identification of several previously ambiguous sources. Bright
optical counterparts exist for 40 of the X-ray sources, of which 33 are
consistent with early-type stars (MV < -2, B-V < 0.2), and are the subject
of a companion paper to the reference paper. The results point to an
underlying HMXB population density up to double that of active systems. The
full catalog of 394 point sources is presented in this table; detailed
analyses of the source timing and spectral properties are available in the
reference paper.
The aim-points for these Chandra observations were as follows: DF1 had
J2000.0 coordinates of 00 53 34.50 -72 26 43.2 and DF2 had
J2000.0 coordinates of 00 50 41.40 -73 16 10.3.
SMCWINGCXO Catalog
The authors have detected 523 X-ray sources in a survey of the Small
Magellanic Cloud (SMC) Wing with the Chandra X-ray Observatory. By
cross-correlating the X-ray data with optical and near-infrared catalogs,
they have found 300 matches. Using a technique that combines X-ray colors
and X-ray to optical flux ratios, they have been able to assign preliminary
classifications to 265 of the objects. The identifications include 4 pulsars,
1 high-mass X-ray binary (HMXB) candidate, 34 stars and 185 active galactic
nuclei (AGN). In addition, the authors have classified 32 sources as hard
AGN which are likely absorbed by local gas and dust, and 9 soft AGN whose
nature is still unclear. Considering the abundance of HMXBs discovered so far
in the Bar of the SMC the number that have been detected in the Wing is low.
Observations in the Wing of the SMC were made from 2005 July to 2006 March
with Chandra. The survey consisted of 20 fields, with exposure times ranging
from 8.6 - 10.3 ks. X-ray parameters for 523 sources detected in the Wing of
the SMC with Chandra are presented. For each source equatorial coordinates,
positional error, net counts (total counts minus background counts) in the
0.5 - 8.0 keV band, signal-to-noise of the detection and source flux in the
0.5 - 8.0 keV band are given. The median, compressed median and normalized
quartile ratio of the photon energy distribution, determined using quantile
analysis, are given for sources with three or more counts. For the sources
that have optical counterparts the V- and R-band magnitudes, B-V color,
X-ray to optical flux ratios based on the V- and R-band magnitudes, and a
preliminary classification for the sources are given.
SPICESCXO Catalog
This table contains the first results on field X-ray sources detected in a
deep, 184.7 ks observation with the Advanced CCD Imaging Spectrometer
(ACIS-I) on the Chandra X-Ray Observatory. The observations target the Lynx
field (J2000.0 RA = 08h 48m and Dec = +44d 54') of SPICES, the Spectroscopic
Photometric Infrared-Chosen Extragalactic Survey, which contains three known
X-ray-emitting clusters at redshifts of z = 0.57, 1.26, and 1.27. Not
including the known clusters, in the 17' x 17' ACIS-I field the authors
detect 132 sources in the 0.5 - 2 keV (soft) X-ray band down to a 2.1-sigma
limiting flux of ~ 1.7 x 10-16 erg/cm2/s and 11 sources in the 2 - 10 keV
(hard) X-ray band down to a 2.1-sigma limiting flux of ~ 1.3 x 10-15
erg/cm2/s. The combined catalog contains a total of 153 X-ray sources, of
which 42 are detected only in the soft band and 21 are detected only in the
hard band.
Confirming previous Chandra results, the authors find that the fainter
sources have harder X-ray spectra, providing a consistent solution to the
long-standing "spectral paradox". From deep optical and near-infrared
follow-up data, 77% of the X-ray sources have optical counterparts to I = 24,
and 71% of the X-ray sources have near-infrared counterparts to Ks = 20.
Four of the 24 sources in the near-IR field are associated with extremely red
objects (EROs; I - Ks >= 4). The authors have obtained spectroscopic
redshifts with the Keck telescopes of 18 of the Lynx Chandra sources. These
sources comprise a mix of broad-lined active galaxies, apparently normal
galaxies, and two late-type Galactic dwarfs. Intriguingly, one Galactic
source (number 72) is identified with an M7 dwarf exhibiting non-transient,
hard X-ray emission. Thirteen of the Chandra sources are located within
regions for which the authors have Hubble Space Telescope imaging. Nine of
the sources are detected, showing a range of morphologies: several show
compact cores embedded within diffuse emission, while others are spatially
extended showing typical galaxy morphologies. Two of the Chandra sources in
this subsample appear to be associated with mergers.
ACIS-I observations of the Lynx field were obtained on 2000 May 3 (65 ks;
OBS-ID 1708) and 2000 May 4 (125 ks; OBS-ID 927). Time intervals with
background rates larger than 3 sigma over the quiescent value of ~ 0.30
counts s-1 per chip in the 0.3 - 10 keV band were removed. This procedure
gave 60.7 ks of effective exposure out of the first observation and 124 ks
out of the second, for a total of 184.7 ks. The two observations are almost
coincident on the sky, so that the total coverage is 298 arcmin2. The aim
point for the observations was RA = 08h 48m 54.79s, Dec = +44d 54' 32.9"
(J2000.0), and both exposures were obtained in the faint mode when ACIS was
at a temperature of -120 C. The Galactic absorbing column for this field is
NH = 2 x 1020 cm-2. The position angle of the observations was 258.45
degrees.
Cosmology-dependent parameters are calculated for two models: an Einstein-de
Sitter (EdS) universe consistent with previous work in this field (H0 = 50
h50 km s-1 Mpc-1, OmegaM = 1, and OmegaLambda = 0) and the dark
energy cosmology (DEC) universe favored by recent work on high-redshift
supernovae and fluctuations in the cosmic microwave background (H0 = 65 km
s-1 Mpc-1, OmegaM = 0.35, and OmegaLambda = 0.65).
SSA22CXO Catalog
This table contains the main X-ray point-source catalog for a deep ~400-ks
Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22
field. The observations were centred on a z = 3.09 protocluster, which is
populated by Lyman break galaxies (LBGs), Lyman-alpha emitters (LAEs) and
extended Lyman-alpha-emitting blobs (LABs). The survey reached ultimate
(3 count) sensitivity limits of ~5.7 x 10-17 and ~3.0 x 10-16 erg
cm-2 s-1 for the 0.5-2 and 2-8 keV bands, respectively (corresponding
to L(2-10 keV) ~ 5.7 x 1042 erg s-1 and L(10-30 keV) ~ 2.0 x 1043
erg s-1 at z = 3.09, respectively, for an assumed photon index of Gamma
= 1.4). These limits make SSA22 the fourth deepest extragalactic Chandra
survey yet conducted, and the only one focused on a known high-redshift
structure. In total, the authors detect 297 X-ray point sources and identify
one obvious bright extended X-ray source (not included in the current table)
over a ~330 arcmin2 region. In addition to the X-ray data, the authors
provide all available optical spectroscopic redshifts and near-infrared
and mid-infrared photometry available for their sources. The basic X-ray
and infrared properties of their Chandra sources indicate a variety of
source types, although absorbed active galactic nuclei (AGN) appear to
dominate. In total, they have identified 12 X-ray sources (either via optical
spectroscopic redshifts or LAE selection) at z = 3.06 - 3.12 that are likely
to be associated with the SSA22 protocluster. These sources have X-ray and
multiwavelength properties that suggest they are powered by AGN with 0.5 -
8 keV luminosities in the range of ~ 1043 - 1045 erg s-1. The authors
have analysed the AGN fraction of sources in the protocluster as a function
of local LAE source density and find suggestive evidence for a correlation
between AGN fraction and local LAE source density (at the ~96 per cent
confidence level), implying that supermassive black hole growth at z ~3 is
strongest in the highest density regions.
SWIRECXO Catalog
This table contains results from deep combined observations with
Spitzer and Chandra of the Spitzer Wide-Area Infrared Extragalactic Survey
(SWIRE) in the ELAIS N1 region. This survey was used to investigate the nature
of the faint X-ray and IR sources in common, to identify active galactic
nucleus (AGN)/starburst diagnostics, and to study the sources of the X-ray
and cosmic infrared backgrounds (XRB and CIRB). In the 17' x 17' area of the
Chandra ACIS-I image there were approximately 3400 SWIRE near-IR sources with
4-sigma detections in at least two Infrared Array Camera (IRAC) bands and 988
sources detected at 24 micron (um) with the Multiband Imaging Photometer
(MIPS) brighter than a 24-um flux S_24 ~ 0.1 mJy. Of these, 102 IRAC and 59
MIPS sources have Chandra counterparts, out of a total of 122 X-ray sources
present in the area with 0.5 - 8 keV flux > 10-15 erg cm^-2 s^-1.
The SWIRE ELAIS N1 field was imaged by the IRAC multiband camera on Spitzer in
2004 January and with MIPS in early 2004 February. The observations were
centered at the position (16h 00m, +59d 01'). The X-ray observations were
taken as part of the ELAIS Deep X-ray Survey (EDXS) and are described in
detail in Manners et al. (2003, MNRAS, 343, 293). For this analysis, the
Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of 75 ks centered
on (16h 10m 20.11s, +54d 33' 22.3") (J2000.0) in the ELAIS N1 region. The aim
point was focused on the ACIS-I chips, which consist of four CCDs arranged in
a 2 x 2 array covering an area of 16.9' x 16.9' (286 square arcmin). Bad pixels
and columns were removed, and data were filtered to eliminate high background
times (due to strong solar flares), leaving 71.5 ks of good data after
filtering. Counts-to-photon calibration assumed a standard power-law model
spectrum with photon index Gamma = 1.7.
Sources were detected to flux levels of 2.3 x 10^-15 erg s^-1 cm^-2 in
the 0.5 - 8 keV band, 9.4 x 10^-16 erg s^-1 cm^-2 in the 0.5 - 2 keV band, and
5.2 x 10^-15 erg s^-1 cm^-2 in the 2 - 8 keV band. Sources are detectable to
these flux limits over 90% of the nominal survey area. For this analysis,
the authors used sources detected in the full band of ACIS-I only, of which
there are 122 in the N1 region. Of the 102 sources in common between Chandra
and SWIRE, 83 have significant detections in the separate soft X-ray band
(0.5 - 2 keV) and 64 are detected in the hard (2 - 8 keV) band.
A simple near-neighbor search was performed to cross-correlate the Spitzer and
Chandra source catalogs within the Chandra ACIS-I chip image, using a d = 5"
search radius (roughly the quadratic sum of the astrometric errors). All
together, the authors found reliably associated counterparts for 102 of the
122 Chandra sources (84% in total). The vast majority of these were detected
with the IRAC channels 1 and 2 (3.6 and 4.5 um): 100 of the 122 Chandra
sources in each case. As many as 59 Chandra objects are reliably associated
with MIPS 24 um sources (all of them having IRAC counterparts), and just 1 had
a MIPS 70 um counterpart. Of the 102 Spitzer-identified Chandra sources, three
turned out to correspond to Galactic stars on the basis of their position on
color-magnitude plots and optical morphology and were excluded from the
subsequent analysis (and this table).
SWIRELHCXO Catalog
The authors have carried out a moderate-depth (70 ks), contiguous 0.7
square degrees Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE
Legacy Survey coincident with a completed, ultra-deep VLA survey with deep
optical and near-infrared imaging in-hand. The primary motivation is to
distinguish starburst galaxies and active galactic nuclei (AGNs), including
the significant, highly obscured (log NH > 23 cm-2) subset. Chandra has
detected 775 X-ray sources to a limiting broadband (0.3 - 8 keV) flux of ~4
x 10-16 erg cm-2 s-1. This table contains the X-ray catalog, fluxes,
hardness ratios, and multi-wavelength fluxes. The log N versus log S agrees
with those of previous surveys covering similar flux ranges. The Chandra and
Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have
infrared (IR) or optical counterparts, and 333 have MIPS 24-micron detections.
There are four optical-only X-ray sources and four with no visible optical/IR
counterpart. The very deep (~2.7 microJansky rms) VLA data yield 251 (>
4 sigma) radio counterparts, 44% of the X-ray sources in the field. The
authors confirm that the tendency for lower X-ray flux sources to be harder
is primarily due to absorption. As expected, there is no correlation between
observed IR and X-ray fluxes. Optically bright, type 1, and red AGNs lie
in distinct regions of the IR versus X-ray flux plots, demonstrating the
wide range of spectral energy distributions in this sample and providing
the potential for classification/source selection. Many optically bright
sources, which lie outside the AGN region in the optical versus X-ray plots
(fr/fx > 10), lie inside the region predicted for red AGNs in IR versus
X-ray plots, consistent with the presence of an active nucleus. More than
40% of the X-ray sources in the VLA field are radio-loud using the classical
definition of RL. The majority of these are red and relatively faint in the
optical so that the use of RL to select those AGNs with the strongest radio
emission becomes questionable. Using the 24-micron to radio flux ratio (q24)
instead results in 13 of the 147 AGNs with sufficient data being classified
as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs
based on optical surveys. The authors conclude that q24 is a more reliable
indicator of radio-loudness. Use of RL should be confined to the optically
selected type 1 AGN.
TRIFIDCXO Catalog
This table contains a list of the Trifid Nebula (M 20) X-Ray point
sources detected by the Chandra X-ray Observatory (CXO) in an observation
carried out on 2002 June 13. The Trifid Nebula, a young star-forming H II
region, was observed for 16 hr by the Advanced CCD Imaging Spectrometer
imaging array, ACIS-I, detector. 304 X-ray sources were detected, 30% of
which are hard sources (defined as those sources having a 0.5-2.0 keV to
2.0-8.0 keV hardness ratio > -0.2) and 70% of which have near-infrared
counterparts.
ULXNGCAT Catalog
One hundred and seven ultraluminous X-ray sources (ULXs) with
0.3-10.0 keV luminosities in excess of 1039 erg s-1 are identified in a
complete sample of 127 nearby galaxies. The sample includes all galaxies within
14.5 Mpc above the completeness limits of both the Uppsala Galaxy Catalogue
and the Infrared Astronomical Satellite survey. The galaxy sample spans all
Hubble types, a four-decade range in mass, 7.5 < log (M/Msun) < 11.4, and in
star formation rate, 0.0002 < SFR(Msun yr-1) <= 3.6. ULXs are detected in
this sample at rates of one per 3.2 x 1010 Msun, one per ~0.5 Msun yr-1
star formation rate, and one per 57 Mpc3 corresponding to a luminosity
density of ~2 x 1037 erg s-1 Mpc-3. At these rates, the authors estimate
as many as 19 additional ULXs remain undetected in fainter dwarf galaxies
within the survey volume. An estimated 14 objects, or 13%, of the 107 ULX
candidates are expected to be background sources. The differential ULX
luminosity function shows a power-law slope alpha ~ -0.8 to -2.0 with an
exponential cutoff at ~20 x 1039 erg s-1 with precise values depending on
the model and on whether the ULX luminosities are estimated from their observed
numbers of counts or, for a subset of candidates, from their spectral shapes.
Extrapolating the observed luminosity function predicts at most one very
luminous ULX, LX ~ 1041 erg s-1, within a distance as small as 100 Mpc.
The luminosity distribution of ULXs within the local universe cannot account
for the recent claims of luminosities in excess of 2 x 1041 erg s-1,
requiring a new population class to explain these extreme objects.
VLACDFSCAT Catalog
This table contains some of the results from 20 and 6 cm VLA deep
observations of the Chandra Deep Field-South (CDF-S), including the Extended
CDF-S (E-CDF-S). In the reference paper, the authors discuss the radio
properties of 266 cataloged radio sources, of which 198 are above a 20-cm
completeness level reaching down to 43 microJanskies (uJy) at the center of
the field. Survey observations made at 6 cm over a more limited region cover
the original CDF-S to a comparable level of sensitivity as the 20-cm
observations. Of 266 cataloged radio sources, 52 have X-ray counterparts in
the CDF-S and a further 37 have counterparts in the E-CDF-S area not covered
by the 1 Ms exposure. Using a wide range of material, the authors have found
optical or infrared counterparts for 254 radio sources, of which 186 have
either spectroscopic or photometric redshifts. Three radio sources have no
apparent counterpart at any other wavelength. Measurements of the 20-cm radio
flux density at the position of each CDF-S X-ray source detected a further 30
radio sources (not included in this table) above a conservative 3-sigma
detection limit. X-ray and sub-millimeter observations have been traditionally
used as a measure of AGN and star formation activity, respectively. These new
observations probe the faint end of both the star formation and radio
galaxy/AGN population, as well as the connection between the formation and
evolution of stars and SMBHs. Both of the corresponding gravitational and
nuclear fusion-driven energy sources can lead to radio synchrotron emission.
AGN and radio galaxies dominate at high flux densities. Although emission
from star formation becomes more prominent at the microJansky levels reached
by deep radio surveys, even for the weakest sources, an apparent significant
contribution from low-luminosity AGN as well as from star formation is still
found.
Notice that are 319 entries in this table corresponding to the 266 catalogued
radio sources, due to the fact that some of these sources have multiple
components. In such cases, the composite source as well as each of its
components are listed as separate entries, e.g., source 7 which has 3
components (A, B and C) has 4 entries in this table.
VLAECDFSOI Catalog
This table contains a sample of 883 sources detected in a deep Very Large
Array (VLA) survey at 1.4 GHz in the Extended-Chandra Deep Field South
(E-CDFS). The reference paper focuses on the identification of their optical
and infrared (IR) counterparts. The authors use a likelihood-ratio technique
that is particularly useful when dealing with deep optical images to minimize
the number of spurious associations. They find a reliable counterpart for 95%
of their radio sources. Most of the counterparts (74%) are detected at optical
wavelengths, but there is a significant fraction (21%) that are only detectable
in the IR. Combining newly acquired optical spectra with data from the
literature, the authors are able to assign a redshift to 81% of the identified
radio sources (37% spectroscopic). They also investigate the X-ray properties
of the radio sources using the Chandra 4 Ms and 250 ks observations. In
particular, the authors use a stacking technique to derive the average
properties of radio objects undetected in the Chandra images. The results of
their analysis are collected in this new catalog containing the position of
the optical/IR counterpart, the redshift information, and the X-ray fluxes.
It is the deepest multi-wavelength catalog of radio sources, which will be
used for future study of this galaxy population.
The E-CDFS was observed at 1.4 GHz with the VLA between 2007 June and
September (Miller et al. 2008, ApJS, 179, 114). The mosaic image covered an
area of about 34 by 34 arcminutes with near-uniform sensitivity. The typical
rms is 7.4 microJy for a 2.8 by 1.6 arcseconds beam. The second data release
(N. Miller et al. 2012, in preparation) provides a new source catalog with a
5-sigma point-source detection limit, for a total of 883 sources. The median
value of the distribution is 58.5 microJy and the median signal-to-noise
ratio (S/N) is 7.6. The authors note that ~ 90% of the sample has a flux
density below 1 mJy, a regime where radio-quiet AGNs and star-forming
galaxies (SFGs) become the dominant populations
VLULXCAT Catalog
Using Chandra archive data, the authors conducted a thorough survey of
luminous X-ray sources. They directly analyzed about 9400 Chandra ACIS
observations and cross-correlated the detected X-ray sources with 77,000
galaxies within a distance of 250 Mpc. The final catalog includes 119 unique
luminous X-ray source candidates with LX > 3 x 1040 erg/s from 93
galaxies or 41 HLX candidates with LX > 1 x 1041 erg/s from 35 galaxies.
The authors derive a moderate contamination rate due to foreground or
background sources. In the reference paper, they also cross-correlate the
catalog with FIRST, perform variability and periodicity tests, and analyze
one HLX candidate in particular. This catalog could be a starting point to
perform follow-up observations.
In order to know whether an X-ray source falls within a particular galaxy,
for each galaxy, the authors collected its center's RA, Dec, distance, and
D25 isophotal info, which includes major axis length, minor axis length,
and the position angle of the major axis from the PGC2003 Catalog (Paturel et
al. 2003, A&A, 412, 45), which includes the full RC3 catalog and has all of
the necessary parameters except for distance. The authors restricted the
minimum major axis length to be 10 arcseconds, and collected their distances
from NED as much as possible. Their final sample includes 77,000 galaxies
within 250 Mpc.
The authors used all of the Chandra ACIS data in TE mode that were released
before 2014, which includes 9400 ObsIDs. A roughly linear relation between
the flux and count rate derived by PIMMS 4.6b was established assuming a
power-law spectral shape and galactic foreground extinction (Kalberla et al.
2005, A&A, 440, 775). Any source with a PIMMS luminosity larger than 5 x
1039 erg s-1 would be recalculated by the CIAO script model flux assuming
a power-law index of 1.7 in the 0.3 - 8.0 keV energy band. After the
recalculation, 1,809 X-ray sources with Lx > 3 x 1040 erg s-1 falling
within 640 D25 contours covered by 905 ObsIDs were picked out. A large
fraction of the 1,809 sources are galactic nuclei and some of them are
repeated. Only off-nuclear sources are considered in this paper. In addition,
the centers of the galaxies given by PGC2003 are not necessarily precise and
the specific environments of the 1,809 sources are different. Therefore, the
authors visually checked the Chandra and DSS images simultaneously, since
two-band inspection can help to exclude the nuclear sources, bright knots,
and extended sources. X-ray sources with clear DSS features would be dropped
because, for a source with a visual magnitude <20 and a distance >30 Mpc, its
absolute magnitude would be brighter than -12.4, which is beyond the limit of
the brightest star clusters.
W40SFRCXO Catalog
The young stellar cluster illuminating the W40 H II region, one of
the nearest massive star-forming regions (SFRs), has been observed with the
ACIS detector on board the Chandra X-ray Observatory. Due to its high
obscuration, this is a poorly studied stellar cluster with only a handful
of bright stars visible in the optical band, including three OB stars
identified as primary excitation sources. The authors detect 225 X-ray sources,
of which 85% are confidently identified as young stellar members of the region.
Two potential distances of the cluster, 260 pc and 600 pc, are used in the
paper. Supposing the X-ray luminosity function of SFRs to be universal, it
supports a 600 pc distance as a lower limit for W40 and a total population of
at least 600 stars down to 0.1 Msun under the assumption of a coeval
population with a uniform obscuration. In fact, there is strong spatial
variation in Ks-band-excess disk fraction and non-uniform obscuration due to
a dust lane that is identified in absorption in optical, infrared, and X-ray.
The dust lane is likely part of a ring of material which includes the molecular
core within W40. In contrast to the likely ongoing star formation in the dust
lane, the molecular core is inactive. The star cluster has a spherical
morphology, an isothermal sphere density profile, and mass segregation down to
1.5 Msun. However, other cluster properties, including a <= 1 Myr age
estimate and ongoing star formation, indicate that the cluster is not
dynamically relaxed. X-ray diffuse emission and a powerful flare from
a young stellar object are also reported in the reference paper.
WD1CXO Catalog
The nature of the X-ray point source population within the young massive
cluster Westerlund 1 (Wd 1) is investigated. Chandra X-ray Observatory (CXO)
observations were used to determine the X-ray properties of emitters within
Wd 1, while a comprehensive multi-wavelength dataset was employed to constrain
their nature. Wd 1 (l=339.5, b=-0.4) was observed with the CXO Advanced CCD
Spectrometer Spectroscopic array on 2005 May 22 for 18 ks (sequence 6283) and
2005 June 20 for 42 ks (sequence 5411). 241 sources were found above a
sensitivity threshold that corresponded to a 10-6 chance per PSF element of
detecting a spurious source. X-ray emission from a multitude of different
stellar sources within Wd 1, including both evolved high mass and low-mass
pre-MS stars, is found.
XBOOTES Catalog
The XBootes table contains the X-Ray point source catalog
from a Chandra survey of the 9 square degrees Bootes field of the
NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126
separate contiguous ACIS-I observations each of approximately 5000 s in
duration. These unique Chandra observations allowed the authors to search for
large-scale structure and to calculate X-ray source statistics over a wide,
contiguous field of view with arcsecond angular resolution and uniform
coverage. Optical spectroscopic follow-up observations and the rich NDWFS
data set will allow the authors to identify and classify these X-ray-selected
sources. Using wavelet decomposition, they have detected 4642 point sources
with n >= 2 counts. In order to keep their detections ~ 99% reliable, they
have limited their list to sources with n >= 4 counts. For a 5000 s
observation and assuming a canonical unabsorbed active galactic nucleus (AGN)
type X-ray spectrum, a 4 count on-axis source corresponds to a flux of 4.7
x 10^-15 ergs cm^-2 s^-1 in the soft (0.5-2 keV) band, 1.5 x 10^-14
ergs cm^-2 s^-1 in the hard (2-7 keV) band, and 7.8 x 10^-15 ergs cm^-2 s^-1
in the full (0.5-7 keV) band. The full 0.5-7 keV band n >= 4 count list
contained in this HEASARC table has 3293 point sources. In addition to the
point sources, 43 extended sources (not included in this HEASARC table) have
been detected, consistent with the depth of these observations
and the number counts of clusters. Presented here in the X-ray point source
catalog for the XBootes survey are the source positions, X-ray fluxes,
hardness ratios, and their uncertainties, for the 3293 sources with >= 4
counts in the full band.
XBOOTESOID Catalog
The XBootes Survey is a 5 ks Chandra survey of the Bootes Field of the NOAO
Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the
largest (9.3 square degrees) contiguous region imaged in X-ray with
complementary deep optical and near-infrared (near-IR) observations. The
authors present a catalog of the optical counterparts to the 3213 X-ray point
sources detected in the XBootes survey. Using a Bayesian identification
scheme, they successfully identified optical counterparts for 98% of the
X-ray point sources. The optical colors suggest that the optically detected
galaxies are a combination of z < 1 massive early-type galaxies and bluer
star-forming galaxies whose optical AGN emission is faint or obscured,
whereas the majority of the optically detected point sources are likely
quasars over a large redshift range. This large-area, X-ray-bright, optically
deep survey enables the authors to select a large subsample of sources (773)
with high X-ray to optical flux ratios (fX/fo > 10). These objects are
likely high-redshift and/or dust-obscured AGNs. These sources have generally
harder X-ray spectra than sources with 0.1 < fX/fo < 10. Of the 73 X-ray
sources with no optical counterpart in the NDWFS catalog, 47 are truly
optically blank down to R ~ 25.5 (the average 50% completeness limit of the
NDWFS R-band catalogs). These sources are also likely to be high-redshift
and/or dust-obscured AGNs.
The 9.3 square degrees region of sky chosen to match the area covered with
the NDWFS was observed by ACIS-I on the Chandra X-Ray Observatory over a 2
week time interval in 2003 March and April. The data were taken in 126
separate pointings, each observed for ~ 5 ks. The CIAO 3.0.2 wavelet
detection algorithm (wavdetect; Freeman et al. 2002) was used to detect X-ray
sources in the total (0.5 - 7.0 keV) band data. A probability threshold of 5
x 10-5 was chosen as the best compromise between maximizing the completeness
while minimizing the number of spurious detections. The X-ray catalog
comprises 3293 unique X-ray sources with >= 4 counts in the total-band images
(Paper II). The authors expect only ~ 35 of these sources to be spurious in
the full survey (Paper II). For the matching with cataloged optical
counterparts, the authors only considered the 3213 X-ray sources that overlap
with the NDWFS area. The authors include all multiply matched sources with
>1% probability of being the correct optical counterpart.
This table contains the X-ray and optical characteristics of the matched
optical/X-ray catalog for the Chandra sources in the XBootes and NDWFS
survey, and is Version 1.0, dated 21st June 2005.
XDEEP2 Catalog
This table contains the X-ray point-source catalog produced from the Chandra
Advanced CCD Imaging Spectrometer (ACIS-I) observations of the combined ~3.2
deg2 DEEP2 (XDEEP2) survey fields, which consist of four ~ 0.7 - 1.1 deg2
fields. The combined total exposures across all four XDEEP2 fields range from
~ 10 ks to 1.1 Ms. The authors detect X-ray point sources in both the
individual ACIS-I observations and the overlapping regions in the merged
(stacked) images. They find a total of 2976 unique X-ray sources within the
survey area with an expected false-source contamination of ~ 30 sources (<~
1%). In their paper, the authors present the combined log N-log S
distribution of sources detected across the XDEEP2 survey fields and find
good agreement with the Extended Chandra Deep Field and Chandra-COSMOS fields
to f_(X,0.5-2keV)_ ~ 2 x 10-16 erg cm-1 s-1. Given the large survey
area of XDEEP2, they additionally place relatively strong constraints on the
log N-log S distribution at high fluxes (f_(X,0.5-2keV) ~ 3 x 10-14 erg
cm-1 s-1), and find a small systematic offset (a factor ~ 1.5) toward
lower source numbers in this regime, when compared to smaller area surveys.
The number counts observed in XDEEP2 are in close agreement with those
predicted by X-ray background synthesis models. Additionally, the authors
present a Bayesian-style method for associating the X-ray sources with
optical photometric counterparts in the DEEP2 catalog (complete to RAB <
25.2) and find that 2126 (~ 71.4% +/- 2.8%) of the 2976 X-ray sources
presented here have a secure optical counterpart with a <~ 6% contamination
fraction. The present table provides the DEEP2 optical source properties
(e.g., magnitude, redshift) as part of the X-ray-optical counterpart catalog.
XSHZAGNCXO Catalog
This table contains the results from an analysis of the largest high-redshift
(z > 3) X-ray-selected active galactic nucleus (AGN) sample to date,
combining the Chandra Cosmological Evolution Survey and Chandra
Multi-wavelength Project surveys and doubling the previous samples. The
sample comprises 209 X-ray-detected AGNs, over a wide range of rest-frame
2-10 keV luminosities log LX = 43.3 - 46.0 erg/s. X-ray hardness ratios
show that ~39 per cent of the sources are highly obscured, NH > 1022
cm-2, in agreement with the ~37 per cent of type-2 AGNs found in this
sample based on their optical classification. For ~26 per cent of objects,
there are mismatched optical and X-ray classifications. Utilizing the
1/Vmax method, the authors confirm that the comoving space density of all
luminosity ranges of AGNs decreases with redshift above z > 3 and up to z ~
7. With a significant sample of AGNs (N = 27) at z > 4, it is found that both
source number counts in the 0.5-2 keV band and comoving space density are
consistent with the expectation of a luminosity-dependent density evolution
(LDDE) model at all redshifts, while they exclude the luminosity and density
evolution (LADE) model. The measured comoving space density of type-1 and
type-2 AGNs shows a constant ratio between the two types at z > 3. These
results for both AGN types at these redshifts are consistent with the
expectations of LDDE model.
The high-redshift AGN sample used in this work has been selected from the
C-COSMOS X-ray catalog, combining the spectroscopic and photometric
information available from the identification catalogue of X-ray C-COSMOS
sources (Civano et al. 2011, ApJ, 741, 91; 2012, ApJS, 201, 30) and the ChaMP
(Chandra Multi-wavelength Project) X-ray catalog using only the 323 ChaMP
ObsIDs overlapping with Sloan Digital Sky Survey (SDSS; Richards et al. 2006,
AJ, 131, 2766) DR5 imaging.