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2561. ChaMPlane X-ray sources in the Galactic bulge

ID:: ivo://CDS.VizieR/J/ApJ/685/463
Title:: ChaMPlane X-ray sources in the Galactic bulge
Short Name:: J/ApJ/685/463
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We 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 our Chandra Multiwavelength Plane Survey. We use 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. We 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. We identify one candidate quiescent low-mass X-ray binary with a subgiant companion; we note that this object may also be an RS CVn system. We report the discovery of three new X-ray-detected cataclysmic variables (CVs) in the direction of the Galactic center (at distances <~2kpc). 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 ~200pc. We discuss several possible reasons for this observed excess.

2562. CHAMP/SDSS Nearby Low-Luminosity AGN Catalog

ID:: ivo://nasa.heasarc/champsdssa
Title:: CHAMP/SDSS Nearby Low-Luminosity AGN Catalog
Short Name:: CHAMPSDSSA
Date:: 28 Feb 2025
Publisher:: NASA/GSFC HEASARC
Description:: 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'). This table was created by the HEASARC in January 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/705/1336/">CDS Catalog J/ApJ/705/1336/</a> file table1.dat. This is a service provided by NASA HEASARC .

2563. ChaMP serendipitous galaxy cluster survey

ID:: ivo://CDS.VizieR/J/ApJ/645/955
Title:: ChaMP serendipitous galaxy cluster survey
Short Name:: J/ApJ/645/955
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multiwavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13deg^2^, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about 10^-14^ergs/cm^2^/s, with a median cluster core radius of 21". For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO 4m MOSAIC g', r', and i' imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore- and background contamination and provides photometric redshifts to z~0.7. From the overlapping 6.1deg^2^ X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog).

2564. ChaMP X-ray point source catalog

ID:: ivo://CDS.VizieR/J/ApJS/169/401
Title:: ChaMP X-ray point source catalog
Short Name:: J/ApJS/169/401
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalog with ~6800 X-ray sources detected in 149 Chandra observations covering ~10deg^2^. The full ChaMP catalog sample is 7 times larger than the initial published ChaMP catalog. The exposure time of the fields in our sample ranges from 0.9 to 124ks, corresponding to a deepest X-ray flux limit of f_0.5-8.0_=9x10^-16^ergs/cm^2^/s. The ChaMP X-ray data have been 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. To best utilize the ChaMP catalog, we also present the source reliability, detection probability, and positional uncertainty.

2565. Chandra ACIS GSG Point-Like X-Ray Source Catalog

ID:: ivo://nasa.heasarc/cxogsgsrc
Title:: Chandra ACIS GSG Point-Like X-Ray Source Catalog
Short Name:: CXOGSGSRC
Date:: 28 Feb 2025
Publisher:: NASA/GSFC HEASARC
Description:: 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. This table was created by the HEASARC in March 2017 primarily based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/224/40/">CDS Catalog J/ApJS/224/40/</a> file table5.dat, the catalog of X-ray point sources in the Chandra ACIS Survey. The positional information for these sources was taken from <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/224/40/">CDS Catalog J/ApJS/224/40/</a> file table3.dat, the list of separation detections for these X-ray sources, using the first listed detection in each case. This is a service provided by NASA HEASARC .

2566. Chandra ACIS Survey for X-Ray AGN in Nearby Galaxies

ID:: ivo://nasa.heasarc/chansngcat
Title:: Chandra ACIS Survey for X-Ray AGN in Nearby Galaxies
Short Name:: CHANSNGCAT
Date:: 28 Feb 2025
Publisher:: NASA/GSFC HEASARC
Description:: 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 <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/835/223">CDS Catalog J/ApJ/835/223</a> files table1.dat, table2.dat and table4.dat. This is a service provided by NASA HEASARC .

2567. Chandra ACIS survey in 383 nearby galaxies. I.

ID:: ivo://CDS.VizieR/J/ApJS/192/10
Title:: Chandra ACIS survey in 383 nearby galaxies. I.
Short Name:: J/ApJS/192/10
Date:: 21 Oct 2021
Publisher:: CDS
Description:: By 2007 December 14, 383 galaxies within 40Mpc with isophotal major axis above 1arcmin had been observed by 626 public Chandra/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 are applied to the 626 ACIS observations and lead to the detection of 28099 point sources, which belong to 17599 independent sources. These include 8700 sources observed twice or more and 1000 sources observed 10 times or more, providing us 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 8519 sources within the D_25_ isophotes of 351 galaxies, 3305 sources between the D_25_ and 2D_25_ isophotes of 309 galaxies, and additionally 5735 sources outside 2D_25_ isophotes of galaxies. This survey has produced a uniform catalog, by far the largest, of 11824 X-ray point sources within 2D_25_ isophotes of 380 galaxies. Contamination analysis using the log N-log S relation shows that 74% of sources within 2D_25_ isophotes above 10^39^erg/s, 71% of sources above 10^38^erg/s, 63% of sources above 10^37^erg/s, and 56% of all sources are truly associated with 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 L_X_(0.3-8keV)>=2x10^39^erg/s within D_25_ isophotes, 179 ULXs between D_25_ and 2D_25_ isophotes, and a total of 479 ULXs within 188 host galaxies, with about 324 ULXs truly associated with host galaxies based on the contamination analysis.

2568. Chandra ACIS survey in nearby galaxies. II

ID:: ivo://CDS.VizieR/J/ApJ/829/20
Title:: Chandra ACIS survey in nearby galaxies. II
Short Name:: J/ApJ/829/20
Date:: 21 Oct 2021
Publisher:: CDS
Description:: Based on the recently completed Chandra/ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library of 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm with good statistics that the XLF slope flattens from lenticular ({alpha}{\sim}1.50{\pm}0.07) to elliptical ({\sim}1.21{\pm}0.02), to spirals ({\sim}0.80{\pm}0.02), to peculiars ({\sim}0.55{\pm}0.30), and to irregulars ({\sim}0.26{\pm}0.10). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosities for different types of galaxies. A radial dependency is found for ellipticals, with a flatter XLF slope for sources located between D_25_ and 2D_25_, suggesting the XLF slopes in the outer region of early-type galaxies are dominated by low-mass X-ray binaries in globular clusters. This study shows that the ULX rate in early-type galaxies is 0.24{\pm}0.05 ULXs per surveyed galaxy, on a 5{sigma} confidence level. The XLF for ULXs in late-type galaxies extends smoothly until it drops abruptly around 4x10^40^erg/s, and this break may suggest a mild boundary between the stellar black hole population possibly including 30M{\sun} black holes with super-Eddington radiation and intermediate mass black holes.

2569. Chandra ACIS survey of M33 (ChaSeM33)

ID:: ivo://CDS.VizieR/J/ApJS/174/366
Title:: Chandra ACIS survey of M33 (ChaSeM33)
Short Name:: J/ApJS/174/366
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We present an overview of the Chandra ACIS Survey of M33 (ChASeM33): A Deep Survey of the Nearest Face-on Spiral Galaxy. The 1.4Ms survey covers the galaxy out to R~18'(~4kpc). These data provide the most intensive, high spatial resolution assessment of the X-ray source populations available for the confused inner regions of M33. The initial source catalog, arising from ~2/3 of the expected survey data, includes 394 sources significant at the 3{sigma} confidence level or greater, down to a limiting luminosity (absorbed) of ~1.6x10^35^ergs/s (0.35-8.0keV). The hardness ratios of the sources separate those with soft, thermal spectra such as supernova remnants from those with hard, nonthermal spectra such as X-ray binaries and background active galactic nuclei. Emission extended beyond the Chandra point-spread function is evident in 23 of the 394 sources. Cross-correlation of the ChASeM33 sources against previous catalogs of X-ray sources in M33 results in matches for the vast majority of the brighter sources and shows 28 ChASeM33 sources within 10" of supernova remnants identified by prior optical and radio searches. This brings the total number of such associations to 31 out of 100 known supernova remnants in M33.

2570. Chandra ACIS Survey of Nearby Galaxies X-Ray Point Source Catalog

ID:: ivo://nasa.heasarc/chngpscliu
Title:: Chandra ACIS Survey of Nearby Galaxies X-Ray Point Source Catalog
Short Name:: CHNGPSCLIU
Date:: 28 Feb 2025
Publisher:: NASA/GSFC HEASARC
Description:: 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. This table was created by the HEASARC in March 2011 based on the electronic version of Table 4 of the reference paper which was obtained from the Astrophysical Journal web site. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .

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2561. ChaMPlane X-ray sources in the Galactic bulge

2562. CHAMP/SDSS Nearby Low-Luminosity AGN Catalog

2563. ChaMP serendipitous galaxy cluster survey

2564. ChaMP X-ray point source catalog

2565. Chandra ACIS GSG Point-Like X-Ray Source Catalog

2566. Chandra ACIS Survey for X-Ray AGN in Nearby Galaxies

2567. Chandra ACIS survey in 383 nearby galaxies. I.

2568. Chandra ACIS survey in nearby galaxies. II

2569. Chandra ACIS survey of M33 (ChaSeM33)

2570. Chandra ACIS Survey of Nearby Galaxies X-Ray Point Source Catalog

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