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2601. Chandra Deep Field-South survey: 7Ms sources
ID:
ivo://CDS.VizieR/J/ApJS/228/2
Title:
Chandra Deep Field-South survey: 7Ms sources
Short Name:
J/ApJS/228/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present X-ray source catalogs for the ~7Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2arcmin^2^. Utilizing wavdetect for initial source detection and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0.5-7.0keV, 0.5-2.0keV, and 2-7keV. A supplementary source catalog is also provided, including 47 lower-significance sources that have bright (K_s_<=23) near-infrared counterparts. We identify multiwavelength counterparts for 992 (98.4%) of the main-catalog sources, and we collect redshifts for 986 of these sources, including 653 spectroscopic redshifts and 333 photometric redshifts. Based on the X-ray and multiwavelength properties, we identify 711 active galactic nuclei (AGNs) from the main-catalog sources. Compared to the previous ~4Ms CDF-S catalogs, 291 of the main-catalog sources are new detections. We have achieved unprecedented X-ray sensitivity with average flux limits over the central ~1arcmin^2^ region of ~1.9x10^-17^, 6.4x10^-18^, and 2.7x10^-17^erg/cm^2^/s in the three X-ray bands, respectively. We provide cumulative number-count measurements observing, for the first time, that normal galaxies start to dominate the X-ray source population at the faintest 0.5-2.0keV flux levels. The highest X-ray source density reaches ~50500deg^-2^, and 47%+/-4% of these sources are AGNs (~23900deg^-2^).
2602. Chandra deep protocluster survey
ID:
ivo://CDS.VizieR/J/MNRAS/400/299
Title:
Chandra deep protocluster survey
Short Name:
J/MNRAS/400/299
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present X-ray point-source catalogues for a deep ~400ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z=3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Ly{alpha} emitters (LAEs) and extended Ly{alpha}-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ~5.7x10^-17^ and ~3.0x10^-16^erg/cm^2^/s for the 0.5-2 and 2-8keV bands, respectively (corresponding to L_2-10keV_~5.7x10^42^erg/s and L_10-30keV_~2.0x10^43^erg/s at z=3.09, respectively, for an assumed photon index of {GAMMA}=1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ~330arcmin^2^ region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources.
2603. Chandra Deep Survey of the HDF-N
ID:
ivo://CDS.VizieR/J/ApJ/554/742
Title:
Chandra Deep Survey of the HDF-N
Short Name:
J/ApJ/554/742
Date:
21 Oct 2021
Publisher:
CDS
Description:
A deep X-ray survey of the Hubble Deep Field-North (HDF-N) and its environs is performed using data collected by the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. Currently a 221.9ks exposure is available, the deepest ever presented, and here we give results on X-ray sources located in the 8.6'x8.7' area covered by the Caltech Faint Field Galaxy Redshift Survey (the "Caltech area"). This area has (1) deep photometric coverage in several optical and near-infrared bands; (2) extensive coverage at radio, submillimeter, and mid-infrared wavelengths; and (3) some of the deepest and most complete spectroscopic coverage ever obtained. It is also where the X-ray data have the greatest sensitivity; the minimum detectable fluxes in the 0.5-2keV (soft) and 2-8keV (hard) bands are ~1.3x10^-16^ and ~6.5x10^-16^ergs/cm^2^/s, respectively.
2604. Chandra DF obscured & Compton-thick AGNs. I. Variability
ID:
ivo://CDS.VizieR/J/ApJ/877/5
Title:
Chandra DF obscured & Compton-thick AGNs. I. Variability
Short Name:
J/ApJ/877/5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed X-ray spectral analysis of 1152 active galactic nuclei (AGNs) selected in the Chandra Deep Fields (CDFs), in order to identify highly obscured AGNs (N_H_>10^23^cm^-2^). By fitting spectra with physical models, 436 (38%) sources with L_X_>10^42^erg/s are confirmed to be highly obscured, including 102 Compton-thick (CT) candidates. We propose a new hardness ratio measure of the obscuration level that can be used to select highly obscured AGN candidates. The completeness and accuracy of applying this method to our AGNs are 88% and 80%, respectively. The observed log N-log S relation favors cosmic X-ray background models that predict moderate (i.e., between optimistic and pessimistic) CT number counts. Nineteen percent (6/31) of our highly obscured AGNs that have optical classifications are labeled as broad-line AGNs, suggesting that, at least for part of the AGN population, the heavy X-ray obscuration is largely a line-of-sight effect, i.e., some high column density clouds on various scales (but not necessarily a dust-enshrouded torus) along our sight line may obscure the compact X-ray emitter. After correcting for several observational biases, we obtain the intrinsic N_H_ distribution and its evolution. The CT/highly obscured fraction is roughly 52% and is consistent with no evident redshift evolution. We also perform long-term (~17yr in the observed frame) variability analyses for 31 sources with the largest number of counts available. Among them, 17 sources show flux variabilities: 31% (5/17) are caused by the change of N_H_, 53% (9/17) are caused by the intrinsic luminosity variability, 6% (1/17) are driven by both effects, and 2 are not classified owing to large spectral fitting errors.
2605. Chandra/ELAIS mid-infrared sources
ID:
ivo://CDS.VizieR/J/MNRAS/355/97
Title:
Chandra/ELAIS mid-infrared sources
Short Name:
J/MNRAS/355/97
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a cross-correlation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep X-ray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15{mu}m catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of ~19 per cent in the 15{mu}m flux range 0.8-6mJy. We have co-added the hard X-ray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source cross-correlation fraction with the XMM-Newton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the mid-infrared galaxy population. The low dust-enshrouded AGN fraction in ELAIS implied by the number of cross-identifications between the ELAIS mid-infrared sample and the Chandra point sources is encouraging for the use of mid-infrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Compton-thick AGN.
2606. Chandra Extended Deep Field South Survey Point Source Catalog
ID:
ivo://nasa.heasarc/chanextdfs
Title:
Chandra Extended Deep Field South Survey Point Source Catalog
Short Name:
ChanDFSS
Date:
28 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the combined point-source catalogs for the Extended Chandra Deep Field- South (E-CDF-S) survey. The E-CDF-S consists of four contiguous 250 ks Chandra observations covering an approximately square region of total solid angle ~0.3 square degrees, which flank the existing ~1 Ms Chandra Deep Field-South (CDF-S). The survey reaches sensitivity limits of ~1.1 x 10&lt;sup&gt;-16&lt;/sup&gt; and ~6.7 x 10&lt;sup&gt;-16&lt;/sup&gt; ergs cm&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt; for the 0.5-2.0 and 2-8 keV bands, respectively. 762 distinct X-ray point sources are detected within the E-CDF-S exposure; 589 of these sources are new (i.e., not previously detected in the ~1 Ms CDF-S). This brings the total number of X-ray point sources detected in the E-CDF-S region to 915 (via the E-CDF-S and ~1 Ms CDF-S observations). Source positions are determined using matched-filter and centroiding techniques; the median positional uncertainty is ~0.35&quot;. The basic X-ray and optical properties of these sources indicate a variety of source types, although absorbed active galactic nuclei (AGNs) seem to dominate. In addition to the main Chandra catalog, this table contains the supplementary source catalog with 33 lower-significance X-ray point sources that have bright optical counterparts (R &lt; 23 mag). These sources generally have X-ray-to-optical flux ratios expected for normal and starburst galaxies, which lack a strong AGN component. The basic number-count results for the main Chandra catalog are in good agreement with the ~1 Ms CDF-S for sources with 0.5-2.0 and 2-8 keV fluxes greater than 3 x 10&lt;sup&gt;-16&lt;/sup&gt; and 1 x 10&lt;sup&gt;-15&lt;/sup&gt; ergs cm&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;, respectively. This HEASARC table contains 809 entries: 762 entries corresponding to the 762 sources listed in the main catalog (Table 2 of the published paper), 14 sources from the cross-field source list (Table 3) which give properties for sources which were detected in more than one observational sources, e.g. there are two entries for the source with source_number = 367, one entry coming from the main catalog, the other entry from the cross-field catalog, and 33 entries corresponding to the 33 sources in the supplementary, optically bright source catalog (Table 6). The HEASARC has created a new parameter called source_type to identify from which of these 3 original tables any given entry comes from; it is set to &#39;main&#39;, &#39;crossfield&#39; and &#39;supplement&#39; for entries from Tables 2, 3, and 6, respectively. This online catalog was created by the HEASARC in January 2006 based on machine-readable versions of tables 2, 3, and 6 from the paper which were obtained from the ApJ website. This is a service provided by NASA HEASARC .
2607. Chandra Galactic Bulge Survey
ID:
ivo://CDS.VizieR/J/MNRAS/458/4530
Title:
Chandra Galactic Bulge Survey
Short Name:
J/MNRAS/458/4530
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b=1.5{deg} above and below the Galactic Centre, spanning (lxb)=(6{deg}x1{deg}). The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{alpha} filters. The catalogue is complete down to r'=20.2 and i'=19.2mag; the mean 5{sigma} depth is r'=22.5 and i'=21.1mag. The mean root-mean-square residuals of the astrometric solutions is 0.04-arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and nd candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~10 0 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4{sigma} X-ray error circle. This analysis yields 1480 potential counterparts (~90 per cent of the sample). 584 counterparts have saturated photometry (r'<=17, i'<=16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' -band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.
2608. Chandra Galactic Bulge Survey Full X-Ray Point Source Catalog
ID:
ivo://nasa.heasarc/changbscat
Title:
Chandra Galactic Bulge Survey Full X-Ray Point Source Catalog
Short Name:
CHANGBSCAT
Date:
28 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the Chandra source list for the entire area of the Galactic Bulge Survey (GBS) based on the lists provided in Jonker et al. (2011, ApJ, 194, 18: Paper I) and Jonker et al. (2014, ApJS, 210, 18: Paper II). The previous version of this table, based solely on the data presented in Paper I, contained the Chandra source list based on the first three-quarters of the GBS that had been observed as of the date of writing of that paper. Among the goals of the GBS are constraining the neutron star (NS) equation of state and the black hole (BH) mass distribution via the identification of eclipsing NS and BH low-mass X-ray binaries (LMXBs). The latter goal will, in addition, be obtained by significantly enlarging the number of BH systems for which a BH mass can be derived. Further goals include constraining X-ray binary formation scenarios, in particular the common envelope phase and the occurrence of kicks, via source-type number counts and an investigation of the spatial distribution of X-ray binaries, respectively. The GBS targets two strips of 6 degrees by 1 degrees (12 deg&lt;sup&gt;2&lt;/sup&gt; in total), one above (1&lt;sup&gt;o&lt;/sup&gt; &lt; b &lt; 2&lt;sup&gt;o&lt;/sup&gt;) and the other below (-2&lt;sup&gt;o&lt;/sup&gt; &lt; b &lt; -1&lt;sup&gt;o&lt;/sup&gt;) the Galactic plane in the direction of the Galactic center at X-ray, optical and near-infrared wavelengths. By avoiding the Galactic plane (-1&lt;sup&gt;o&lt;/sup&gt; &lt; b &lt; 1&lt;sup&gt;o&lt;/sup&gt;) the authors limit the influence of extinction on the X-ray and optical emission but still sample relatively large number densities of sources. The survey is designed such that a large fraction of the X-ray sources can be identified from their optical spectra. The X-ray survey, by design, covers a large area on the sky while the depth is shallow, using 2 ks per Chandra pointing. In this way, the authors maximize the predicted number ratio of (quiescent) LMXBs to cataclysmic variables. The survey is approximately homogeneous in depth to a 0.5-10 keV flux of 7.7 x 10&lt;sup&gt;-14&lt;/sup&gt; erg cm&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;. As of Paper I, the authors had covered about three-fourths (8.3 deg&lt;sup&gt;2&lt;/sup&gt;) of the projected survey area with Chandra observations providing 1234 unique X-ray sources. In Paper II, the authors find 424 additional X-ray sources in the 63 Chandra observations that they report on there. In the papers, the authors discuss the characteristics and the X-ray variability of the brightest of the sources as well as the radio properties from existing radio surveys. They point out an interesting asymmetry in the number of X-ray sources as a function of their Galactic l and b coordinates which is probably caused by differences in average extinction towards the different parts of the GBS survey area. This table was originally ingested by the HEASARC in June 2011 based on an electronic version of Table 3 from Paper I which was obtained from the ApJS web site. The current version of this table was ingested by the HEASARC in January 2014 based on &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/210"&gt;CDS catalog J/ApJS/210&lt;/a&gt;,18 file cxogbs.dat, which appears to be the combination of an Table 3 from Paper I with Table 1 from Paper II. This is a service provided by NASA HEASARC .
2609. Chandra HRC source in M31
ID:
ivo://CDS.VizieR/J/ApJ/578/114
Title:
Chandra HRC source in M31
Short Name:
J/ApJ/578/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a 47ks observation of the Andromeda galaxy, M31, using the High Resolution Camera of the Chandra X-Ray Observatory. We detect 142 point sources spanning 3 orders of magnitude in luminosity, from L_X_=2x10^35^ to 2x10^38^erg/s in the 0.1-10keV band. The X-ray source location accuracy is better than 1" in the central regions of the galaxy. One source lies within 1.3" of SN 1885 but does not coincide with the UV absorption feature identified as the supernova remnant.
2610. Chandra J1030 Redshift identification
ID:
ivo://CDS.VizieR/J/A+A/656/A117
Title:
Chandra J1030 Redshift identification
Short Name:
J/A+A/656/A117
Date:
22 Feb 2022
Publisher:
CDS
Description:
We publicly release the spectroscopic and photometric redshift catalog of the sources detected with Chandra in the field of the z=6.3 quasar SDSS J1030+0525. This is currently the fifth deepest X-ray field, and reaches a 0.5-2keV flux limit f_0.5-2_=6x10^-17^erg/s/cm^2^. By using two independent methods, we measure a photometric redshift for 243 objects, while 123 (51%) sources also have a spectroscopic redshift, 110 of which coming from an INAF-Large Binocular Telescope (LBT) Strategic Program. We use the spectroscopic redshifts to determine the quality of the photometric ones, and find it in agreement with that of other X-ray surveys which used a similar number of photometric data-points. In particular, we measure a sample normalized median absolute deviation sigma_NMAD_=1.48xmedia(||z_phot_-z_spec_||/(1+z_spec_)=0.065. We use these new spectroscopic and photometric redshifts to study the properties of the Chandra J1030 field. We observe several peaks in our spectroscopic redshift distribution between z=0.15 and z=1.5, and find that the sources in each peak are often distributed across the whole Chandra field of view. This evidence confirms that X-ray selected AGN can efficiently track large-scale structures over physical scales of several Mpc. Finally, we computed the Chandra J1030 z>3 number counts: while the spectroscopic completeness at high-redshift of our sample is limited, our results point towards a potential source excess at z>=4, which we plan to either confirm or reject in the near future with dedicated spectroscopic campaigns.

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