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. This database was created by the HEASARC in January 2002 based on CDS Catalog J/ApJS/80/531, tables gxatlas.dat and gxfluxes.dat. This is a service provided by NASA HEASARC .

The catalog of 4195 optically confirmed Sunyaev-Zel'dovich (SZ) selected galaxy clusters were detected with signal-to-noise > 4 in 13,211 deg² of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multi-frequency matched filter to 98- and 150-GHz maps constructed from ACT observations obtained from 2008-2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 < z < 1.91 (median z = 0.52). The catalog contains 222 z > 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ-signal vs. mass scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M_500c > 3.8 x 10¹⁴M_sol, evaluated at z=0.5, for clusters detected at signal-to-noise ratio > 5 in maps filtered at an angular scale of 2.40. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ-signal mass-scaling relation, such as the Dark Energy Survey (4566 deg²), the Hyper Suprime-Cam Subaru Strategic Program (469 deg²), and the Kilo Degree Survey (825 deg²). This HEASARC database table was ingested in February 2021. It contains the ACT DR5 SZ cluster catalog obtained from the LAMDBA website (https://lambda.gsfc.nasa.gov/product/act/actpol_dr5_szcluster_catalog_info.cfm#catalog). This is a service provided by NASA HEASARC .

In a correlation study of the ROSAT All-Sky Survey Bright Source Catalog (RASS-BSC, CDS Cat. , the HEASARC table RASSBSC) with the Catalogue of Principal Galaxies (PGC, CDS Cat. , the HEASARC table PGC2003), 904 X-ray sources were found that possess possible extragalactic counterparts within a search radius of 100 arcseconds. A visual screening process was applied to classify the reliability of the correlations. 547 correlations have been quoted as reliable identifications. From these, 349 sources are known to be active galaxies. Although for the other sources no hints for activity were found in the literature, 69% of those for which we have distances show X-ray luminosities exceeding those of normal galaxies, a clear sign that these galaxies also own hitherto unreported X-ray active components. Some objects are located inside or in the direction of a known group or cluster of galaxies. Their X-ray flux may therefore be in part affected by hot gas emission. In the paper, luminosity and log N-log S distributions are used to characterize different subsamples. Nuclei that are both optically and X-ray active are found predominantly in spirals. Two special source samples are defined, one with candidates for X-ray emission from hitherto unknown groups or clusters of galaxies, and one with high X-ray luminosity sources, that are likely candidates to possess hitherto unreported active galactic nuclei. Besides a compilation of X-ray and optical parameters, X-ray overlays on optical images for all the objects are also supplied as part of this work. This table contains 1124 optical galaxy entries for the 904 relevant X-ray candidates/counterparts from the RASS. Besides a compilation of X-ray and optical parameters for each source, the results of an identification screening are also given. The 904 optical images with X-ray overlay contours (xID_nnn.ps.gz) used in the screening process are added for each user's own judgement of the reliability of the associations. This table was created by the HEASARC in March 2012 based on CDS catalog J/A+A/378/30 file table1.dat, the list of PGC galaxies identified as possible counterparts to RASS Bright Source Catalog X-ray sources. This is a service provided by NASA HEASARC .

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, L_X, 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. L_X-star formation rate (SFR) correlation or have higher L_X 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. L_X-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 L_X 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 L_X values can be observed due to strong XRB variability. This table was created by the HEASARC in May 2019 based upon the CDS Catalog J/ApJ/817/95 file table3.dat This is a service provided by NASA HEASARC .

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 L_X 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 L_X 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/L_Edd, opposite to the trend which is exhibited by high-z AGN (quasars). The turning point in the Gamma - L/L_Edd LLAGN + quasars relation occurs near Gamma ~ 1.5 and L/L_Edd ~ 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/L_Edd 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/L_Edd >~ 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 nH_Gal. 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'). This table was created by the HEASARC in January 2012 based on CDS Catalog J/ApJ/705/1336/ file table1.dat. This is a service provided by NASA

The authors have compiled a sample of X-ray-selected galaxy groups and clusters from the XMM-Newton Serendipitous Source Catalog (2XMMi-DR3) with optical confirmation and redshift measurement from the Sloan Digital Sky Survey (SDSS). In their paper, they present an analysis of the X-ray properties of this new sample with particular emphasis on the X-ray luminosity-temperature (L_X - T) relation. The X-ray cluster candidates were selected from the 2XMMi-DR3 catalog in the footprint of the SDSS-DR7. The authors developed a finding algorithm to search for overdensities of galaxies at the positions of the X-ray cluster candidates in the photometric redshift space and to measure the redshifts of the clusters from the SDSS data. For optically confirmed clusters with good quality X-ray data, they derived the X-ray flux, luminosity, and temperature from proper spectral fits, while the X-ray flux for clusters with low-quality X-ray data was obtained from the 2XMMi-DR3 catalogue. The detection algorithm provides the photometric redshift of 530 galaxy clusters. Of these, 310 clusters have a spectroscopic redshift for at least one member galaxy. About 75 percent of the optically confirmed cluster sample are newly discovered X-ray clusters. Moreover, 301 systems are known as optically selected clusters in the literature while the remainder are new discoveries in X-ray and optical bands. The optically confirmed cluster sample spans a wide redshift range 0.03 to 0.70 (median z = 0.32). In this paper, they present the catalog of X-ray-selected galaxy groups and clusters from the 2XMMi/SDSS galaxy cluster survey. The catalog has two subsamples: (i) a cluster sample comprising 345 objects with their X-ray spectroscopic temperature and flux from the spectral fitting; (these objects are identified by having values for the table_sample parameter of 1 in this HEASARC implementation of the catalog) and (ii) a cluster sample consisting of 185 systems with their X-ray flux from the 2XMMi-DR3 catalog, because their X-ray data are insufficient for spectral fitting (these objects are identified by having values for the table_sample parameter of 2 herein). For each cluster, the catalog also provides the X-ray bolometric luminosity and the cluster mass at R₅₀₀ based on scaling relations and the position of the likely brightest cluster galaxy (BCG). The updated L_X - T relation of the current sample with X-ray spectroscopic parameters is presented in the paper. The authors found the slope of the L_X - T relation to be consistent with published ones. They see no evidence for evolution in the slope and intrinsic scatter of the L_X - T relation with redshift when excluding the low-luminosity groups. This catalog of X-ray selected galaxy clusters and groups supersedes and subsumes the first release of the 2XMMi/SDSS Galaxy Cluster Survey, comprising 175 clusters of galaxies, which was presented in Takey et al. (2011, A&A, 534, A120). This table was created by the HEASARC in October 2013 based on CDS catalog J/A+A/558/A75 files table1.dat and table2.dat. This is a service provided by NASA HEASARC .

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. This table was created by the HEASARC in September 2017 based upon the CDS Catalog J/ApJ/835/223 files table1.dat, table2.dat and table4.dat. This is a service provided by NASA HEASARC .

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 (µm) 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. This table was created by the HEASARC in Match 2012 based on CDS Catalog J/ApJ/708/584 file table2.dat. This is a service provided by NASA HEASARC .