- ID:
- ivo://nasa.heasarc/chanulxcat
- Title:
- Chandra Archive Of Galaxies Ultraluminous X-Ray Source Catalog
- Short Name:
- CHANULXCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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 10<sup>39</sup> 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 N<sub>H</sub> = 2.24 x 10<sup>21</sup> atoms cm<sup>-2</sup>, 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. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/154/519">CDS catalog J/ApJS/154/519</a> file table2.dat. This is a service provided by NASA HEASARC .
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Search Results
- ID:
- ivo://nasa.heasarc/cbfgrxecxo
- Title:
- Chandra Bulge Field X-Ray Point Source Catalog
- Short Name:
- CBFGRXECXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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<sup>-14</sup> erg/cm<sup>2</sup>/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<sup>-5</sup>, implying that one false positive detection would be expected at every 4 x 10<sup>4</sup> 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 (P<sub>B</sub>). The PS is defined as the background-subtracted source counts (C<sub>net</sub>) divided by its background counts normalized by the area. P<sub>B</sub> 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 P<sub>B</sub> <= 1.0 x 10<sup>-2</sup>. As a result, they obtained 2002 valid point sources. This table was created by the HEASARC in December 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/766/14">CDS catalog J/ApJ/766/14</a> file table2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ccosmosoid
- Title:
- Chandra COSMOS (C-COSMOS) Survey Optical/IR Counterparts Catalog
- Short Name:
- CCOSMOSOID
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8-Ms, Chandra program that has imaged the central 0.9 deg<sup>2</sup> of the COSMOS field down to limiting depths of 1.9 x 10<sup>-16</sup> erg/cm<sup>2</sup>/s in the soft (0.5-2 keV) band, 7.3 x 10<sup>-16</sup> erg/cm<sup>2</sup>/s in the hard (2-10 keV) band, and 5.7 x 10<sup>-16</sup> erg/cm<sup>2</sup>/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 <a href="ccosmoscat.html">CCOSMOSCAT</a> for the the surveyed X-ray point sources. This table was created by the HEASARC in December 2012, based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/201/30">CDS Catalog J/ApJS/201/30</a> file catalog.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ccosmphotz
- Title:
- Chandra COSMOS (C-COSMOS) Survey Photometric Redshift Catalog
- Short Name:
- CCOSMPHOTZ
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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+Z<sub>spec</sub>)] ~ 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 deg<sup>2</sup> 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 (H<sub>AB</sub> = 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. This table was created by the HEASARC in November 2011 based on an electronic version of Table 4 from the reference paper which was obtained from the ApJ website. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ccosmoscat
- Title:
- Chandra COSMOS (C-COSMOS) Survey X-Ray Point Source Catalog
- Short Name:
- CCOSMOSCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.5 deg<sup>2</sup> 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 deg<sup>2</sup> area with an effective exposure of ~ 80 ks. The limiting source detection depths are 1.9 x 10<sup>-16</sup> erg cm<sup>-2</sup> s<sup>-1</sup> in the soft (0.5 - 2 keV) band, 7.3 x 10<sup>-16</sup> erg cm<sup>-2</sup> s<sup>-1</sup> in the hard (2 - 10 keV) band, and 5.7 x 10<sup>-16</sup> erg cm<sup>-2</sup> s<sup>-1</sup> 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<sup>-5</sup> (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 deg<sup>2</sup> 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 <a href="https://cosmos.astro.caltech.edu/page/xray/">COSMOS Survey website</a> and at <a href="https://irsa.ipac.caltech.edu/data/COSMOS/">IRSA</a>. 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 <a href="ccosmosoid.html">CCOSMOSOID</a> for the optical and infrared identifications of the surveyed X-ray point sources. This table was created by the HEASARC in November 2009 based on an electronic version of the C-COSMOS Catalog which was obtained from the Astrophysical Journal web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ccosrssfag
- Title:
- Chandra COSMOS Radio-Selected Star-Forming Galaxies and AGN Catalog
- Short Name:
- CCOSRSSFAG
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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. This table was created by the HEASARC in June 2012 based on CDS table J/A+A/542/A16 files table2.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/chandfn2ms
- Title:
- Chandra Deep Field North 2-Megasecond Catalog
- Short Name:
- Chan/DF2N
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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<sup>2</sup>). The on-axis sensitivity limits are ~2.5x10<sup>-17</sup> ergs/cm<sup>2</sup>/s (0.5 - 2.0 keV) and 1.4x10<sup>-16</sup> ergs/cm<sup>2</sup>/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<sup>-1</sup> pixel<sup>-1</sup>, 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. This table was created by the HEASARC in April 2004 based on CDS catalog table J/AJ/126/539/cdfn.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/chandfn1ms
- Title:
- Chandra Deep Field North 1-Megasecond Catalog
- Short Name:
- ChanDF
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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<sup>-17</sup> and ~2 x 10<sup>-16</sup> 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<sup>-2</sup> (at 4.2 x 10<sup>-17</sup> ergs cm<sup>-2</sup> s<sup>-1</sup>) and 4200 (+670, -580) deg<sup>-2</sup> (at 3.8 x 10<sup>-16</sup> ergs cm<sup>-2</sup> s<sup>-1</sup>) are observed in the soft and hard bands, respectively. This online catalog was created by the HEASARC in March 2002 based on a machine-readable version of Table 3 of Brandt et al. (2001) that was obtained from the Astronomical Journal website. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/cdfn2msnew
- Title:
- Chandra Deep Field North 2-Megasecond Improved Point Source Catalog
- Short Name:
- CDFN2MSNEW
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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<sup>-5</sup> 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 K<sub>s</sub> <= 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). This table was created by the HEASARC in August 2016 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/224/15">CDS Catalog J/ApJS/224/15</a> files table3.dat (the main source catalog) and table6.dat (the supplementary source catalog). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/cdfn2msoid
- Title:
- ChandraDeepFieldNorth2-MegasecondOptical&IRCatalog
- Short Name:
- Chan/DF2S
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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 (L<sub>2-8keV</sub> > 10<sup>44</sup> 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 <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/126/539">CDS Catalog <J/AJ/126/539></a>, 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. This table was created by the HEASARC in April 2004 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/126/632/table1a">CDS Catalog J/AJ/126/632/table1a</a>.dat. This is a service provided by NASA HEASARC .
