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301. 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.
302. 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).
303. 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.
304. 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.
305. 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.
306. Chandra COSMOS survey I.
ID:
ivo://CDS.VizieR/J/ApJS/184/158
Title:
Chandra COSMOS survey I.
Short Name:
J/ApJS/184/158
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8Ms, Chandra program that has imaged the central 0.5deg^2^ of the COSMOS field (centered at 10h, +02d) with an effective exposure of ~160ks, and an outer 0.4deg^2^ area with an effective exposure of ~80ks. The limiting source detection depths are 1.9x10^-16^erg/cm2/s in the soft (0.5-2keV) band, 7.3x10^-16^erg/cm2/s in the hard (2-10keV) band, and 5.7x10^-16^erg/cm2/s in the full (0.5-10keV) band. Here we 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 <2x10^-5^ (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 0.5deg^2^ 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 logN-logS curve, with subarcsecond positions, enabling optical and infrared identifications of virtually all sources, as reported in a second companion paper.
307. Chandra Deep Field North Survey. V.
ID:
ivo://CDS.VizieR/J/AJ/122/2810
Title:
Chandra Deep Field North Survey. V.
Short Name:
J/AJ/122/2810
Date:
21 Oct 2021
Publisher:
CDS
Description:
An extremely deep X-ray survey (~1Ms) of the Hubble Deep Field North (HDF-N) and its environs (~450arcmin^2^) has been performed with the Advanced CCD Imaging Spectrometer (ACIS) 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 and 2-8keV flux limits of ~3x10^-17^ and ~2x10^-16^ergs/cm^2^/s, respectively. Here we provide source catalogs, along with details of the observations, data reduction, and technical analysis. Observing conditions, such as background, were excellent for almost all of the exposure. We have detected 370 distinct point sources: 360 in the 0.5-8.0keV band, 325 in the 0.5-2.0keV band, 265 in the 2-8keV band, and 145 in the 4-8keV band. Two new Chandra sources in the HDF-N itself are reported and discussed. Source positions are accurate to within 0.6"-1.7" (at ~90% confidence), depending mainly on the off-axis angle. We also detect two highly significant extended X-ray sources and several other likely extended X-ray sources. We present basic number count results for sources located near the center of the field. Source densities of 7100^+1100^_-940_deg^-2^ (at 4.2x10^-17^ergs/cm^2^/s) and 4200^+670^_580_deg^-2^ (at 3.8x10^-16^ergs/cm^2^/s) are observed in the soft and hard bands, respectively.
308. Chandra Deep Field-South ATLAS 5.5GHz DR2
ID:
ivo://CDS.VizieR/J/MNRAS/454/952
Title:
Chandra Deep Field-South ATLAS 5.5GHz DR2
Short Name:
J/MNRAS/454/952
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new image of the 5.5GHz radio emission from the extended Chandra Deep Field South. Deep radio observations at 5.5GHz were obtained in 2010 and presented in the first data release. A further 76h of integration has since been obtained, nearly doubling the integration time. This paper presents a new analysis of all the data. The new image reaches 8.6{mu}Jy rms, an improvement of about 40% in sensitivity. We present a new catalogue of 5.5GHz sources, identifying 212 source components, roughly 50% more than were detected in the first data release. Source counts derived from this sample are consistent with those reported in the literature for S_5.5GHz_>0.1mJy but significantly lower than published values in the lowest flux density bins (S_5.5GHz_<0.1mJy), where we have more detected sources and improved statistical reliability. The 5.5GHz radio sources were matched to 1.4GHz sources in the literature and we find a mean spectral index of -0.35+/-0.10 for S_5.5GHz_>0.5mJy, consistent with the flattening of the spectral index observed in 5GHz sub-mJy samples. The median spectral index of the whole sample is {alpha}_med_=-0.58, indicating that these observations may be starting to probe the star-forming population. However, even at the faintest levels (0.05<S_5.5GHz_<0.1mJy), 39% of the 5.5GHz sources have flat or inverted radio spectra. Four flux density measurements from our data, across the full 4.5-6.5GHz bandwidth, are combined with those from literature and we find 10% of sources (S_5.5GHz_>~0.1mJy) show significant curvature in their radio spectral energy distribution spanning 1.4-9GHz.
309. Chandra Deep Field South. 1 Ms catalog
ID:
ivo://CDS.VizieR/J/ApJS/139/369
Title:
Chandra Deep Field South. 1 Ms catalog
Short Name:
J/ApJS/139/369
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we present the source catalog obtained from a 942ks exposure of the Chandra Deep Field South (CDFS), using the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-ray Observatory. Eleven individual pointings made between 1999 October and 2000 December were combined to generate the final image used for object detection. Catalog generation proceeded simultaneously using two different methods: a method of our own design using a modified version of the SExtractor algorithm, and a wavelet transform technique developed specifically for Chandra observations. The detection threshold has been set in order to have less than 10 spurious sources, as assessed by extensive simulations. We subdivided the catalog into four sections: the primary list consisting of objects common to the two detection methods, two secondary lists containing sources which were detected by (1) the SExtractor algorithm alone and (2) the wavelet technique alone, and the fourth list consisting of possible diffuse or extended sources. The flux limits at the aimpoint for the soft (0.5-2keV) and hard (2-10keV) bands are 5.5x10^-17^erg/s/cm^2^ and 4.5x10^-16^erg/s/cm^2^, respectively. The total number of sources is 346; out of them, 307 were detected in the 0.5-2keV band, and 251 in the 2-10keV band. We also present optical identifications for the catalogued sources. Our primary optical data are R band imaging from VLT/FORS1 to a depth of R~26.5 (Vega). In regions of the field not covered by the VLT/FORS1 deep imaging, we use R-band data obtained with the Wide Field Imager (WFI) on the ESO-MPI 2.2 m telescope, as part of the ESO Imaging Survey (EIS), which cover the entire X-ray survey. We found that the FORS1/Chandra offsets are small, ~1". Coordinate cross-correlation finds 85% of the Chandra sources covered by FORS1 R to have counterparts within the 3{sigma} error box (>~1.5" depending on off-axis angle and X-ray signal-to-noise). The unidentified fraction of sources, approximately ~10%-15%, is close to the limit expected from the observed X-ray flux to R-band ratio distribution for the identified sample.
310. Chandra Deep Field South: multi-colour data
ID:
ivo://CDS.VizieR/II/253A
Title:
Chandra Deep Field South: multi-colour data
Short Name:
II/253A
Date:
21 Oct 2021
Publisher:
CDS
Description:
Table 3 contains the object catalogue of the COMBO-17 CDFS field. The observations were carried out with the Wide Field Imager (WFI) at the MPG/ESO 2.2-m telescope on La Silla, Chile, between October 1999 and January 2001 in four independent observing runs. The field measures 31.5'x30', is centered on RA=03:32:25, DE=-27:48:50 and contains the Chandra Deep Field South. The table contains 63501 objects found on the deep R-band image cdfs_r.fit by SExtractor with S/N>3. The 5-{sigma} magnitude limit for point sources is Rmag=26.0. Morphological information from the SExtractor measurement is included. Multiple observations in different observing runs of six different filters allow the identification of variable objects. The table contains positions, flags and flux measurements in UBVRI and 12 optical medium-band filters. In addition, we include multi-colour classification, photometric redshifts, luminosity distances and a number of absolute restframe magnitudes in different filters (Johnson, Sloan, Bessell). cdfs_u.fit, cdfs_b.fit, cdfs_v.fit, cdfs_r.fit and cdfs_i.fit are coadded sumframes in UBVRI of the CDFS field. These sumframes are stacked from flat-fielded and cosmic-corrected individual images by applying only full pixel shifts. Therefore, the coordinate frames differ slightly between the images. The coordinates in Table 3 refer to image cdfs_r.fit. The images in BVRI are obtained from observations carried out in observing run D (Oct 1999, see also Note (11) in the byte-by-byte description of table3.dat) while the U-band image is obtained from observing run G (Jan 2001). The exposure times are 14400s (U), 5000s (B), 8400s (V), 15000s (R) and 7550s (I). The intensity levels are given in units of photons hitting the detector (already corrected for the gain of the CCD). The data included here supersede the table2.dat of the COMBO-17 published in 2001 (J/A+A/377/442)