EINGALCAT Catalog
This is a catalog of galaxies observed in the X-ray band with
the Einstein Observatory imaging instruments, the Imaging Proportional
Counter (IPC) and the High Resolution Imager (HRI). The catalog comprises
716 observations of 493 galaxies, including those that were targets of
pointed observations, and galaxies from the Revised Shapley-Ames (RSA)
Catalog of Bright Galaxies and the Second Revised Catalog (RC2) Catalog of
Bright Galaxies that were serendipitously included in Einstein fields,
plus X-ray data on 4 other galaxies (LMC, SMC, M 31 = NGC 224, and M 32 =
NGC 221) taken from the literature, for a total of 720 entries.
A total of 450 of these galaxies were imaged well within the instrumental
fields, resulting in 238 detections and 212 3-sigma upper limits. The other
galaxies were either at the edge of the visible field of view or were
confused with other X-ray sources.
EINGALCLUS Catalog
The Einstein Observatory Clusters of Galaxies Catalog presents the
X-ray characteristics of a sample of 368 clusters of galaxies with redshifts
less than 0.2 which were observed with the Einstein Imaging Proportional
Counter (IPC). For each cluster, the authors measured the 0.5 - 4.5 keV
counting rate and computed the 0.5 - 4.5 keV source luminosity, as well as
the bolometric luminosity within fixed metric radii. They detected 85% of
Abell clusters with z < 0.1, demonstrating that the large majority of these
optically selected clusters are not the results of chance superpositions. For
163 clusters, they measured their X-ray surface brightness profiles and
determined their core radii. For about 230 clusters, they then used either
their measured core radii and beta values, or mean values derived for this
sample, to measure central gas densities and gas masses. They used estimated
or measured cluster gas temperatures, along with the derived gas-density
profiles, to estimate total cluster masses, under the assumptions that the
gas is isothermal and in hydrostatic equilibrium.
EINOPSLGAL Catalog
The Einstein Survey of Optically Selected Galaxies contains the results of a
complete Einstein Imaging Proportional Counter (IPC) X-ray survey of
optically-selected galaxies from the Shapley-Ames (S-A) Catalog (CDS Catalog
<VII/112>), the Uppsala General Catalog (UGC, CDS Catalog <VII/26>) and the
European Southern Observatory (ESO) Catalog (CDS Catalog <VII/115>).
Well-defined optical criteria were used to select the galaxies, and X-ray
fluxes were measured at the optically-defined positions. The result is a
comprehensive list of X-ray detection and upper limit measurements for 1018
galaxies. Of these, 827 galaxies have either independent distance estimates
or radial velocities. Associated optical, redshift, and distance data have
been assembled for these galaxies, and their distances come from a
combination of directly predicted distances and those predicted from the
Faber-Burstein Great Attractor/Virgocentric infall model. The accuracy of the
X-ray fluxes has been checked in three different ways; all are consistent
with the derived X-ray fluxes being of <= 0.1 dex accuracy. In particular,
there is agreement with previously published X-ray fluxes for galaxies in
common with a 1991 study by Roberts et al. (1991ApJS...75..751R) and a 1992
study by Fabbiano et al. (1992ApJS...80..531F, also available at the HEASARC
as a database table called EINGALCAT).
EINSTEIN2E Catalog
This is the Einstein Observatory 2E Catalog of Imaging Proportional Counter
(IPC) X-Ray Sources which was created by the HEASARC from the CDS Catalog
IX/13. This latter catalog was prepared by the CDS in October 1996 based on
the Einline version. It is similar to the HEASARC's IPC source catalog which
the HEASARC created in the early 1990s directly based on Einstein
Observatory Source Catalog tables obtained from the then-extant Astrophysics
Data System distributed data archive. The IPC Catalog contains 6816 entries
compared to 5948 entries in this catalog, notice.
This catalog contains sources with signal-to-noise values of 3.5 and greater
from Einstein IPC observations. Note that a single source may have more than
one entry in this catalog.
EMSS Catalog
This database table contains information from the Einstein Extended Medium
Sensitivity Survey (EMSS) which consists of 835 serendipitous X-ray sources
detected at or above 4 times the rms level in 1435 IPC fields with their
centers located away from the galactic plane. Their limiting sensitivities
range from ~5*10E-14 to ~3*10-12 ergs cm-3 s-1 in the 0.3-3.5keV band. A
total area of 778 square degrees of the high galactic latitude sky (|b|>20)
has been covered. The analysis has been performed using data from the Rev 1
processing system at the CfA. The resulting EMSS catalog is a flux-limited and
homogeneous sample of astronomical objects that can be used for statistical
studies. Additional information is available from the HEASARC.
ETGALXRAY Catalog
This table contains a catalog of X-ray luminosities for 401 early-type
galaxies (and 24 other galaxies which were listed in previuous studies as
early but which have LEDA T-types >= -1.5), of which 136 are based on newly
analysed ROSAT PSPC pointed observations. The remaining luminosities are
taken from the literature and converted to a common energy band, spectral
model and distance scale. In their paper, the authors use this sample to
fit the LX/LB relation for early-type galaxies and find a best-fit
slope for the catalog of ~ 2.2. The authors demonstrate the influence of
group-dominant galaxies on the fit and present evidence that the relation
is not well modeled by a single power-law fit. They also derive estimates
of the contribution to galaxy X-ray luminosities from discrete-sources
and conclude that they provide L(discrete-source-contribution)/LB ~
29.5 erg s-1/LBsun. The authors compare this result with luminosities
from their catalog. Lastly, they examine the influence of environment on
galaxy X-ray luminosity and on the form of the LX/LB relation. They
conclude that although environment undoubtedly affects the X-ray properties
of individual galaxies, particularly those in the centres of groups and
clusters, it does not change the nature of whole populations.
The sample of early-type galaxies was selected from the Lyon-Meudon
Extragalactic Data Archive (LEDA). This catalog at that time contained
information on ~ 100,000 galaxies, of which ~ 40,000 had redshift and
morphological data. Galaxies were selected using the following criteria:
(i) Morphological Type T < -1.5 (i.e. E, E-S0 and S0 galaxies).
(ii) Virgo-corrected recession velocity V <= 9,000 km s-1.
(iii) Apparent Magnitude BT <= 13.5.
The redshift and apparent magnitude restrictions were chosen in order to
minimize the effects of incompleteness on their sample. The LEDA catalogue
is known to be 90 per cent complete at BT = 14.5, so the selection should
be close to statistical completeness. The selection process produced ~
700 objects. The authors then cross-correlated this list with a list of
public ROSAT PSPC pointings. Only pointings within 30 arcminutes of the
target were accepted, as, further off-axis, the PSPC point-spread function
becomes large enough to make analysis problematic. This left 209 galaxies
with X-ray data available.
The authors also added data from previously published catalogs, ROSAT
PSPC All-Sky Survey values from Beuing et al. (1999, MNRAS, 302, 209),
and Einstein IPC values from Fabbiano et al. (1992, ApJS, 80, 531)
and Roberts et al. (1991, ApJS, 75, 751). These other references use a
range of models to fit the data, different wavebands, distances and blue
luminosities. O'Sullivan et al. corrected for these differences by converting
the catalogs to a common set of values, as used for their own results.
All of the X-ray luminosities have been converted to a common format based
on a reliable distance scale (assuming H0 = 75 km s-1 Mpc-1), and
correcting for differences in spectral fitting techniques and waveband.
EXSS Catalog
The Einstein Extended Source Survey (EXSS) catalog contains a list of extended
sources found in the Einstein Observatory Imaging Proportional Counter (IPC)
Database. The source detection algorithm was substantially improved over that
used for the Einstein Medium Sensitivity Survey (EMSS). Sources were searched
for using circular apertures with variable radii of up to 6.1 arcminutes.
Criteria were constructed so as to ascertain which of the detections were
truly diffuse and which of the sizes best approximated each detection.
Using these criteria, a catalog of 1325 extended source candidates at high
galactic latitude (more than 20 degrees from the Galactic Equator) was
produced. Cross-correlating this list with existing source catalogs yielded
a reasonably comprehensive set of identifications for the sources in this
list: over 400 were identified with known clusters of galaxies, while other
objects were identified with galaxies, supernova remnants (SNR), active
galactic nuclei (AGN), and stars. Whereas galaxies and SNR are often truly
extended objects, AGN and stars can appear as extended ojects as a consequence
of their soft X-ray spectra coupled with the broad point-spread function of
the IPC at low energies. A total of 321 objects remain completely
unidentified. Some of these may be heretofore uncatalogued clusters
and groups of galaxies at moderate redshifts.
FPCSFITS Catalog
The FPCSFITS database is a listing of the Focal Plane Crystal Spectrometer
photon event data. It was created in October 1992 and contains one entry for
each of the 436 FPCS FITS files.
HRICFA Catalog
This database table consists of a preliminary source list for the Einstein
Observatory's High Resolution Imager (HRI). The source list, obtained from
EINLINE, the Einstein On-line Service at the Smithsonian Astrophysical
Observatory (SAO), contains basic information about the sources detected
with the HRI.
HRIDEEP Catalog
This database table contains primary HRI source parameters for the 202 HRI
sources found in the Einstein Deep Survey. The Einstein Deep Survey (EDS)
program consisted of very deep X-ray exposures in selected regions of the sky
at high galactic latitude. The main purposes of the survey are to investigate
the nature of the extragalactic X-ray background through direct source counts
at very low flux levels and to study the nature of the very faint X-ray sources
which comprise a significant fraction, if not all, of the soft X-ray
background.
HRIEXO Catalog
The Einstein High Resolution Imager (HRI) consisted of a micro-channel
plate. This database table has been generated at the EXOSAT observatory by
automatically processing all the HRI images. Both the images and detected
sources are available. This catalog has not been cleaned or checked.
Users should beware of two possible problems: (1) spurious detections caused
by extended sources have not been checked, and (2) there may be a one-pixel
offset in some positions. For HRI images, one pixel is one arcsecond.
(The images are rebinned from the original 0.5 arcseconds.)
HRIIMAGE Catalog
The HRIIMAGE database table contains information from the High Resolution
Imager aboard HEAO 2, the Einstein Observatory. Einstein incorporated a
high-resolution X-ray telescope and a focal plane assembly capable of
positioning at its focus one of four instruments: a high-resolution imaging
detector (HRI), a broader-field imaging proportional counter (HRI), a solid
state spectrometer (SSS), and a Bragg crystal spectrometer (FPCS). Einstein
(HEAO 2) was launched on November 13, 1978, and operated successfully until
April 1981.
HRIPHOT Catalog
The HRIPHOT database contains information from the High Resolution Imager
aboard HEAO-2, the Einstein Observatory, in Event List Format. Einstein
incorporated a high-resolution X-ray telescope and a focal plane assembly
capable of positioning at its focus one of four instruments: a high-
resolution imaging detector (HRI), a broader-field imaging proportional
counter (IPC), a solid state spectrometer (SSS), and a Bragg crystal
spectrometer (FPCS). Einstein (HEAO-2) was launched on November 13, 1978,
and operated successfully until April 1981.
IPC Catalog
This database contains information on sources detected with the Einstein
Observatory Image Proportional Counter (IPC), assembled for the Einstein
Observatory Catalog (EOSCAT) of IPC X-ray Sources (2E) and containing over
4000 unique sources (with 6539 separate detections) which were detected with
the IPC at a level of significance greater than 3.5 sigma in the broad
band (0.2-3.5 keV).
This database also contains the list of 277 sources which are known not to
have been included in the Einstein Observatory Source Catalog (flagged by
supplement = 'Y' in this database). Those which were not detected during the
standard Rev1B processing were typically discovered upon visual inspection of
the contour diagrams in the Catalog. Others were detected with Rev1B standard
processing but left out of the Catalog because of short exposure times or
other reasons listed in the "missed_code" field. 258 of these 277 additional
sources have no valid signal to noise ratio (SNR) estimate (values of 0.0),
while 3 others have SNR values of 3.2 and 3.3, notice.
This IPC database is based on NASA Astrophysics Data System (ADS) tables that
were created in 1991 and 1993 and were themselves derived from tables
provided by Dr. D. E. Harris of the Center for Astrophysics at
Harvard-Smithsonian. The HEASARC has a similar catalog in its database
called EINSTEIN2E which comprises a more recent version of the IPC
source list as archived at the NASA Astronomical Data Center (ADC) and
the Center for Astronomical Data at Strasbourg (CDS). EINSTEIN2E has 868
fewer detections than the IPC catalog, notice, for reasons that the HEASARC
is unsure of, but that may imply that some of the detections in IPC are
not reliable. We have retained the IPC database for reasons of completeness,
but caution that detections listed here which have no counterpart in the
EINSTEIN2E Catalog should be treated with caution.
IPCDEEP Catalog
IPCDEEP is created from a table containing basic source parameters for each of
the 178 IPC sources detected by the Einstein Deep Survey. The Einstein Deep
Survey program (EDS) consists of very deep X-ray exposures in selected regions
of the sky at high galactic latitude. The main purposes of the survey are to
investigate the nature of the extragalactic X-ray background through direct
source counts at very low flux levels and to study the nature of the very faint
X-ray sources which comprise a significant fraction, if not all, of the soft
X-ray background.
IPCIMAGE Catalog
The IPCIMAGE database contains information from the Imaging Proportional
Counter aboard HEAO 2, the Einstein Observatory. Einstein incorporated a
high-resolution X-ray telescope and a focal plane assembly capable of
positioning at its focus one of four instruments: a high-resolution imaging
detector (HRI), a broader-field imaging proportional counter (IPC), a solid
state spectrometer (SSS), and a Bragg crystal spectrometer (FPCS). Einstein
(HEAO 2) was launched on November 13, 1978, and operated successfully until
April 1981.
IPCLXLBOL Catalog
Soft X-ray (0.2 - 3.5 keV) measurements for all normal, massive, o-type stars
surveyed with the Einstein Observatory are presented as a catalog containing 89
detections and 176 upper bounds, together with a detailed discussion of the
reduction process. Values of L[x]/L[bol] listed for most stars, range from
10e-5.44 to 10e-7.35; l[x] spans more than 3 orders of magnitude, ranging from
1.5 x 10e31 to 2 x 10e34 ergs se-1. It is noted that at least 30% of o-type
stars are variable in X-rays, but that there is little evidence for new objects
whose X-ray emission might be significantly enhanced by accretion processes
onto a neutron star. For further information, please contact the HEASARC.
IPCOSTARS Catalog
This information, derived from the Einstein X-ray Observatory Catalog of
O-type Stars, by Chlebowski, Harnden and Sciortino, provides information
regarding the Soft X-ray measurements for all normal, massive, O-type stars
serveyed with The Einstein Observatory. More information is available through
the HEASARC.
IPCPHOT Catalog
The IPCPHOT database contains information from the Imaging Proportional
Counter aboard HEAO-2, the Einstein Observatory, in Event List Format.
Einstein incorporated a high-resolution X-ray telescope and a focal
plane assembly capable of positioning at its focus one of four
instruments: a high-resolution imaging detector (HRI), a broader-field
imaging proportional counter (IPC), a solid state spectrometer (SSS),
and a Bragg crystal spectrometer (FPCS). Einstein (HEAO-2) was launched
on November 13, 1978, and operated successfully until April 1981.
IPCSLEW Catalog
This database table contains the list of sources detected in the IPC
Slew Survey. It was created in March 1992 and contains 819 entries.
The original IPC Slew Survey source list was released on CD-ROM and contained
1067 sources. The list was updated in 1991 to remedy a software bug which
omitted a thin slice of RA near 24h; the bug fix yielded 8 additional sources,
to bring the total to 1075. The list, however, was found to contain a large
fraction (10 to 15 percent) of unreliable sources, especially those sources
with <= 5 photons. The unreliable sources were rejected in producing the
latest version of the source list, so that it now has an estimated false source
rate of only 2 percent, and contains 256 fewer sources than the previous
version.
The previous version of the source list, with 1075 sources, has been retained
in a database called OLDIPCSLEW.
IPCULTSOFT Catalog
A survey of the entire Einstein IPC database (a total of 5934
sources) has been carried out in order to select objects with strong
components of ultrasoft X-ray emission (i.e., emission below 0.5 keV).
The selection criteria were based on ratios of counts within three broad
energy bands (i.e., X-ray "colors"). A total of 516 objects have been
selected, with 202 (39%) having been identified through correlations with
other databases. Of the currently identified objects, 45% are active
galactic nuclei, 28% are stellar objects, 6% are "normal" galaxies and
galaxy clusters, and the remaining 21% are "nonstellar" Galactic objects
such as cataclysmic variables, pulsars, and white dwarfs.
The selection of sources for this survey was based on the analysis of
counts in three broad energy bands defined as C1=0.16-0.56 keV,
C2=0.56-1.08 keV, and C3= 1.08-3.5 keV. Ratios of these three bands
constituted X-ray 'colors' which in turn were used to estimate the shape
of the spectrum over the IPC bandpass. Based on models of X-ray spectra
folded through the IPC response function, the following criteria were
determined for the selection of ultrasoft sources: C1>0 and
R1=C2/C1<0.36. These criteria guarantee an intrinsically soft X-ray
spectrum that can be modeled by blackbody temperatures kT<50 keV,
power-law spectral indices of >=2, or thermal plasma temperatures
T<1 MK (million K). Details of the data analysis can be found in
the Thompson et al. (1998) reference.
IPCUNSCRND Catalog
This database table gives access to the IPC unscreened data set, which
includes files in the event list format together with auxiliary files. This
data set was generated by the Einstein Data Center and delivered to the
HEASARC on CD-ROM.
The Einstein Observatory (HEAO-2) operated from November 1978 to April 1981.
Einstein carried the first fully imaging X-ray telescope in space and
operated in pointing mode. The Imaging Proportional Counter had a bandpass of
0.2-3.5 keV and was one of two detectors onboard used for imaging. During the
Einstein lifetime more than 4000 targets were observed with the IPC.
LMCXRAY Catalog
This database table contains 105 "discrete" (i.e., more compact than 1.25
arcminutes) and 9 "large-diameter" (detected using a detection circle
radius of 2 arcminutes) Einstein IPC X-ray sources in the direction of
the Large Magellanic Cloud (LMC) that are tabulated in Tables 2 and 4,
respectively, of Wang et al. (1991, ApJ, 374, 475). For full details
of the data processing and selection used to create this source catalog,
the above reference should be consulted.
MCXC Catalog
The MCXC is the Meta-Catalog of the compiled properties of X-ray detected
Clusters of galaxies. This very large catalog is based on publicly available
ROSAT All Sky Survey (RASS)-based (NORAS, REFLEX, BCS, SGP, NEP, MACS, and
CIZA) and ROSAT serendipitous (160SD, 400SD, SHARC, WARPS, and EMSS) cluster
catalogs. Data have been systematically homogenised to an overdensity of 500,
and duplicate entries from overlaps between the survey areas of the
individual input catalogs have been carefully handled. The MCXC comprises
1743 clusters with virtually no duplicate entries. For each cluster, the MCXC
provides three identifiers, a redshift, coordinates, membership in the
original catalog, and standardised 0.1 - 2.4 keV band luminosity Lx500,
total mass M500, and radius R500, where the 500 suffix means that the
quantity has been calculated up to a standard characteristic radius R500,
the radius within which the mean overdensity of the cluster is 500 times the
critical density at the cluster redshift . The meta-catalog additionally
furnishes information on overlaps between the input catalogs and the
luminosity ratios when measurements from different surveys are available, and
gives notes on individual objects. The MCXC is made available so as to
provide maximum usefulness for X-ray, Sunyaev-Zel'dovich (SZ) and other
multiwavelength studies.
The catalogs and sub-catalogs included in this meta-catalog are listed in
Table 1 of the reference paper, and come from the following references:
Catalog Sub- Reference Title
Catalog or CDS Cat. (Author)
RASS IX/10 ROSAT All-Sky Bright Source Catalog (1RXS)
(Voges+, 1999)
BCS
BCS J/MNRAS/301/881 ROSAT brightest cluster sample - I.
(Ebeling+, 1998)
eBCS J/MNRAS/318/333 Extended ROSAT Bright Cluster Sample
(Ebeling+ 2000)
CIZA X-ray clusters behind the Milky Way
CIZAI ApJ, 580, 774
(Ebeling+, 2002)
CIZAII J/APJ/662/224
(Kocevski+, 2007)
EMSS ApJS, 72, 567 Einstein Extended Medium Sensitivity Survey
(Gioia+, 1990)
EMSS_1994 ApJS, 94, 583
(Gioia & Luppino, 1994)
EMSS_2004 ApJ, 608, 603
(Henry 2004)
MACS ApJ, 553, 668 Massive Cluster Survey
(Ebeling+, 2001)
MACS_MJFV ApJS, 174, 117
(Maughan+, 2008)
MACS_BRIGHT MNRAS, 407, 83
(Ebeling+, 2010)
MACS_DIST ApJ, 661, L33
(Ebeling+, 2007)
NEP NEP J/ApJS/162/304 ROSAT NEP X-ray source catalog
(Henry+, 2006)
NORAS/
REFLEX
NORAS J/ApJS/129/435 NORAS galaxy cluster survey. I.
(Boehringer+, 2000)
REFLEX J/A+A/425/367 REFLEX Galaxy Cluster Survey Cat
(Boehringer+, 2004)
SGP SGP J/ApJS/140/239 Clusters of galaxies around SGP
(Cruddace+, 2002)
SHARC
SHARC_BRIGHT J/ApJS/126/209 Bright SHARC survey cluster catalog
(Romer+, 2000)
SHARC_SOUTH J/MNRAS/341/1093 The Southern SHARC catalog
(Burke+, 2003)
WARPS
WARPSI J/ApJS/140/265 WARPS survey. VI.
(Perlman+, 2002)
WARPSII J/ApJS/176/374 WARPS-II Cluster catalog. VII.
(Horner+, 2008)
160SD
160SD J/ApJ/594/154 160 square degree ROSAT Survey
(Mullis+, 2003)
400SD J/ApJS/172/561 400 square degree ROSAT Cluster Survey
(Burenin+, 2007)
400SD_SER Serendipitous clusters
400SD_NONSER Not entirely serendipitous clusters
MPCRAW Catalog
The Einstein Observatory (also known as HEAO-2 or HEAO-B) was operational
from 1978 November 13 until 1981 April 25 when the Einstein attitude control
system failed. The Monitor Proportional Counter (MPC) was a non-focal plane
instrument that monitored the 1 to 20 keV X-ray flux of the source(s) being
observed simultaneously by the operational focal plane instrument. The MPC
was a collimated proportional counter filled with argon and carbon dioxide.
It had a circular field of view, 1.5 degrees in diameter (FWHM), which was
co-aligned with the telescope. A 1.5 mil Be window sealed the gas in the
detector and shielded the detector from ultraviolet radiation. The active
area of the MPC was 667 square cm. The MPC obtained useful data from 1978
November 19 until 1981 April 17, with the exception of a 3-month period from
1980 Aug 27 to 1980 Dec 08 when operation was intermittent, due to Einstein
Observatory attitude control problems. The characteristics of the MPC have
been described in detail by Gaillardetz et al.(1979) and by Grindlay et al.
(1980).
SMCXRAY Catalog
This database contains the 70 `discrete' (i.e., more compact than a few
arc minutes) Einstein IPC X-ray sources in the direction of
the Small Magellanic Cloud (SMC) that are tabulated in Table 2A
of Wang & Wu (1992, ApJS, 78, 391). For full details about the data
processing and selection criteria used to create the original source catalog,
the above reference should be consulted.
SSS Catalog
This table is the Einstein Solid State Spectrometer catalog of observations
and data products. It incorporates the most recent ice model that is
described in the article on the SSS calibration by Christian, Swank, and
White that appeared in the HEASARC journal, Legacy, No. 1. Also available as
"associated" data products are the quasi-simultaneous observations made by
the Einstein Monitor Proportional Counter. There are 634 distinct SSS
observations in this database, 95% of which have associated MPC data
products. The remaining SSS observations cover time intervals in which all
MPC data was flagged as bad by the pCHIP program that was used to generate
the MPC spectra and lightcurves.
SSSRAW Catalog
The Einstein Observatory (also known as HEAO-2 or HEAO-B) was operational from
1978 November 13 until 1981 April 25 when the attitude control system
failed. The Solid State Spectrometer (SSS) was operated intermittently between
1978 December 1 and 1979 October 22. However, the cryogen cooling for the
detector was used up by about 2 weeks prior to the date of this last
observation, so that the last reliable observation of the SSS is considered to
have occurred on 1979 October 03. The SSSRAW database accesses the raw SSS
data (and the associated monitoring proportional counter, MPC, data), restored
in FITS format at HEASARC from the original machine dependent format data set.
TWOSIGMA Catalog
The X-ray sources from observations made with the Einstein Observatory
(HEAO-2) Imaging Proportional Counter (IPC) that have intensities of 2-sigma
or more above the background are compiled in this catalog. This catalog covers
more sky at fainter flux levels than the Einstein Medium Sensitivity Survey.
Fields with diffuse emission sources such as bright Abell clusters of galaxies
and supernova remnants were excluded. Thus, data within 10 degrees of the
galactic plane as well as fields within the boundaries of the
Magellanic Clouds were excluded. Regions crowded with galactic sources such
as the Orion and Pleiades fiels were also excluded. Excluding redundant fields,
this catalog covers 1850 sq. degrees of the sky.
The generation of the Einstein Two-Sigma Catalog was described in
detail by Moran et al. (1996). Please read this article carefully to ensure
responsible use of the Catalog. Detailed scientific and technical questions
on the contents and methodology of this catalog should be addressed to
the first author, Ed Moran (edhed@igpp.llnl.gov). In particular, it should be
noted that, by design, this catalog contains a significant number of spurious
sources: only 28%, or about 13,000 sources, out of the 46,000 source in the
2-sigma catalog are `real` astrophysical sources, with the remainder of the
sources being spurious ones. Moran et al. show in their paper that performing
cross-correlations of 2-sigma sources with other catalogs is an
effective way of selecting sources in this catalog that are probably real.
