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2571. Chandra and AAOmega observations of Abell 2744
ID:
ivo://CDS.VizieR/J/ApJ/728/27
Title:
Chandra and AAOmega observations of Abell 2744
Short Name:
J/ApJ/728/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
New Chandra X-ray data and extensive optical spectroscopy, obtained with AAOmega on the 3.9m Anglo-Australian Telescope, are used to study the complex merger taking place in the galaxy cluster Abell 2744. Combining our spectra with data from the literature provides a catalog of 1237 redshifts for extragalactic objects lying within 15' of the cluster center. From these, we confirm 343 cluster members projected within 3Mpc of the cluster center. Combining positions and velocities, we identify two major substructures, corresponding to the remnants of two major subclusters. The new data are consistent with a post-core-passage, major merger taking place along an axis that is tilted well out of the plane of the sky, together with an interloping minor merger. Supporting this interpretation, the new X-ray data reveal enriched, low entropy gas from the core of the approaching, major subcluster, lying ~2' north of the cluster center, and a shock front to the southeast of the previously known bright, compact core associated with the receding subcluster. The X-ray morphology of the compact core is consistent with a Bullet-like cluster viewed from within ~45{deg} of the merger axis. An X-ray peak ~3' northwest of the cluster center, with an associated cold front to the northeast and a trail of low entropy gas to the south, is interpreted as the remnant of an interloping minor merger taking place roughly in the plane of the sky. We infer approximate paths for the three merging components.
2572. Chandra and IR study toward IRAS 16562-3959
ID:
ivo://CDS.VizieR/J/ApJ/888/118
Title:
Chandra and IR study toward IRAS 16562-3959
Short Name:
J/ApJ/888/118
Date:
17 Jan 2022 11:46:14
Publisher:
CDS
Description:
We present the results from Chandra X-ray observations, and near- and mid-infrared analysis, using VISTA/VVV and Spitzer/GLIMPSE catalogs, of the high-mass star-forming region IRAS 16562-3959, which contains a candidate for a high-mass protostar. We detected 249 X-ray sources within the ACIS-I field of view. The majority of the X-ray sources have low count rates (<0.638cts/ks) and hard X-ray spectra. The search for YSOs in the region using VISTA/VVV and Spitzer/GLIMPSE catalogs resulted in a total of 636 YSOs, with 74 Class I and 562 Class II YSOs. The search for near- and mid-infrared counterparts of the X-ray sources led to a total of 165 VISTA/VVV counterparts, and a total of 151 Spitzer/GLIMPSE counterparts. The infrared analysis of the X-ray counterparts allowed us to identify an extra 91 Class III YSOs associated with the region. We conclude that a total of 727 YSOs are associated with the region, with 74 Class I, 562 Class II, and 91 Class III YSOs. We also found that the region is composed of 16 subclusters. In the vicinity of the high-mass protostar, the stellar distribution has a core-halo structure. The subcluster containing the high-mass protostar is the densest and the youngest in the region, and the high-mass protostar is located at its center. The YSOs in this cluster appear to be substantially older than the high-mass protostar.
2573. Chandra and near-IR obs. of Cyg OB2
ID:
ivo://CDS.VizieR/J/A+A/464/211
Title:
Chandra and near-IR obs. of Cyg OB2
Short Name:
J/A+A/464/211
Date:
21 Oct 2021
Publisher:
CDS
Description:
The aim of this work is to identify the so far unknown low mass stellar population of the ~2Myr old Cygnus OB2 star forming region, and to investigate the X-ray and near-IR stellar properties of its members. We analyzed a 97.7ks Chandra ACIS-I observation pointed at the core of the Cygnus OB2 region. Sources were detected using the PWDETECT code and were positionally correlated with optical and near- IR catalogs from the literature. Source events were extracted with the Acis E XTRACT package. X-ray variability was characterized through the Kolmogorov-Smirnov test and spectra were fitted using absorbed thermal plasma models. We detected 1003 X-ray sources. Of these, 775 have near-IR counterparts and are expected to be almost all associated with Cygnus OB2 members.
2574. Chandra Archive Of Galaxies Ultraluminous X-Ray Source Catalog
ID:
ivo://nasa.heasarc/chanulxcat
Title:
Chandra Archive Of Galaxies Ultraluminous X-Ray Source Catalog
Short Name:
CHANULXCAT
Date:
25 Apr 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&lt;sup&gt;39&lt;/sup&gt; erg/s, have been identified in 82 galaxies that were observed with Chandra&#39;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&lt;sub&gt;H&lt;/sub&gt; = 2.24 x 10&lt;sup&gt;21&lt;/sup&gt; atoms cm&lt;sup&gt;-2&lt;/sup&gt;, 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 &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/154/519"&gt;CDS catalog J/ApJS/154/519&lt;/a&gt; file table2.dat. This is a service provided by NASA HEASARC .
2575. Chandra Bulge Field X-Ray Point Source Catalog
ID:
ivo://nasa.heasarc/cbfgrxecxo
Title:
Chandra Bulge Field X-Ray Point Source Catalog
Short Name:
CBFGRXECXO
Date:
25 Apr 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&lt;sup&gt;-14&lt;/sup&gt; erg/cm&lt;sup&gt;2&lt;/sup&gt;/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&lt;sup&gt;-5&lt;/sup&gt;, implying that one false positive detection would be expected at every 4 x 10&lt;sup&gt;4&lt;/sup&gt; 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&amp;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&lt;sub&gt;B&lt;/sub&gt;). The PS is defined as the background-subtracted source counts (C&lt;sub&gt;net&lt;/sub&gt;) divided by its background counts normalized by the area. P&lt;sub&gt;B&lt;/sub&gt; 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 &gt;= 1.0 and P&lt;sub&gt;B&lt;/sub&gt; &lt;= 1.0 x 10&lt;sup&gt;-2&lt;/sup&gt;. As a result, they obtained 2002 valid point sources. This table was created by the HEASARC in December 2014 based on &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/766/14"&gt;CDS catalog J/ApJ/766/14&lt;/a&gt; file table2.dat. This is a service provided by NASA HEASARC .
2576. Chandra Carina Complex Project (CCCP) catalog
ID:
ivo://CDS.VizieR/J/ApJS/194/2
Title:
Chandra Carina Complex Project (CCCP) catalog
Short Name:
J/ApJS/194/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of ~14000 X-ray sources observed by the ACIS instrument on the Chandra X-ray Observatory within a 1.42deg^2^ survey of the Great Nebula in Carina, known as the Chandra Carina Complex Project (CCCP). This study appears in a special issue devoted to the CCCP. Here, we describe the data reduction and analysis procedures performed on the X-ray observations, including calibration and cleaning of the X-ray event data, point-source detection, and source extraction. The catalog appears to be complete across most of the field to an absorption-corrected total-band luminosity of ~10^30.7^erg/s for a typical low-mass pre-main-sequence star. Counterparts to the X-ray sources are identified in a variety of visual, near-infrared, and mid-infrared surveys. The X-ray and infrared source properties presented here form the basis of many CCCP studies of the young stellar populations in Carina.
2577. Chandra compact binaries in 47 Tuc
ID:
ivo://CDS.VizieR/J/other/Sci/292.2290
Title:
Chandra compact binaries in 47 Tuc
Short Name:
J/other/Sci/292.
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained high-resolution (<~1") deep X-ray images of the globular cluster 47 Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70-kilosecond exposure of the cluster reveals a centrally concentrated population of faint (L_X_~10^30-33^ergs/s) X-ray sources, with at least 108 located within the central 2'x2.5' and >~half with L_X_<~10^30.5^ergs/s. All 15 millisecond pulsars (MSPs) recently located precisely by radio observations are identified, though 2 are unresolved by Chandra. The X-ray spectral and temporal characteristics, as well as initial optical identifications with the Hubble Space Telescope, suggest that >~50 percent are MSPs, about 30 percent are accreting white dwarfs, about 15 percent are main-sequence binaries in flare outbursts, and only two to three are quiescent low-mass X-ray binaries containing neutron stars, the conventional progenitors of MSPs. An upper limit of about 470 times the mass of the sun is derived for the mass of an accreting central black hole in the cluster. These observations provide the first X-ray ``color-magnitude'' diagram for a globular cluster and census of its compact object and binary population. Observations were made on UT 16.31 - 17.22 March, 2000.
2578. Chandra-COSMOS Bright Source Catalog
ID:
ivo://irsa.ipac/COSMOS/Catalog/CCOSMOS-BSC
Title:
Chandra-COSMOS Bright Source Catalog
Short Name:
CCOSMOS-BSC
Date:
01 Oct 2018 20:27:21
Publisher:
NASA/IPAC Infrared Science Archive
Description:
COSMOS is an astronomical survey designed to probe the formation and evolution of galaxies as a function of cosmic time (redshift) and large scale structural environment. The survey covers a 2 square degree equatorial field with imaging by most of the major space-based telescopes (Hubble, Spitzer, GALEX, XMM, Chandra) and a number of large ground based telescopes (Subaru, VLA, ESO-VLT, UKIRT, NOAO, CFHT, and others). Over 2 million galaxies are detected, spanning 75% of the age of the universe. This is version 2.1 of the C-COSMOS Bright Source Catalog which consists of 1761 sources detected at uniform confidence in the 0.5 - 7 keV band of the Chandra-COSMOS survey. Details of the survey and initial results are found in the C-COSMOS catalog paper (Elvis et al. 2009, Paper I). The methods used to detect sources and generate the catalog are described in detail in Puccetti et al. 2009 (Paper II). Nearly 100%-complete multiwavelength source identification is discussed in Civano et al. 2009 (Paper III).
2579. Chandra COSMOS (C-COSMOS) Survey Optical/IR Counterparts Catalog
ID:
ivo://nasa.heasarc/ccosmosoid
Title:
Chandra COSMOS (C-COSMOS) Survey Optical/IR Counterparts Catalog
Short Name:
CCOSMOSOID
Date:
25 Apr 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&lt;sup&gt;2&lt;/sup&gt; of the COSMOS field down to limiting depths of 1.9 x 10&lt;sup&gt;-16&lt;/sup&gt; erg/cm&lt;sup&gt;2&lt;/sup&gt;/s in the soft (0.5-2 keV) band, 7.3 x 10&lt;sup&gt;-16&lt;/sup&gt; erg/cm&lt;sup&gt;2&lt;/sup&gt;/s in the hard (2-10 keV) band, and 5.7 x 10&lt;sup&gt;-16&lt;/sup&gt; erg/cm&lt;sup&gt;2&lt;/sup&gt;/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 &lt;a href="ccosmoscat.html"&gt;CCOSMOSCAT&lt;/a&gt; for the the surveyed X-ray point sources. This table was created by the HEASARC in December 2012, based on the &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/201/30"&gt;CDS Catalog J/ApJS/201/30&lt;/a&gt; file catalog.dat. This is a service provided by NASA HEASARC .
2580. Chandra COSMOS (C-COSMOS) Survey Photometric Redshift Catalog
ID:
ivo://nasa.heasarc/ccosmphotz
Title:
Chandra COSMOS (C-COSMOS) Survey Photometric Redshift Catalog
Short Name:
CCOSMPHOTZ
Date:
25 Apr 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&lt;sub&gt;spec&lt;/sub&gt;)] ~ 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&lt;sup&gt;2&lt;/sup&gt; 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 &gt; 0.2. These changes are predominantly due to the inclusion of newly available deep H-band^ photometry (H&lt;sub&gt;AB&lt;/sub&gt; = 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 .

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