- ID:
- ivo://CDS.VizieR/J/ApJ/613/279
- Title:
- ACS Virgo Cluster Survey. III. M87
- Short Name:
- J/ApJ/613/279
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ACIS instrument on board the Chandra X-Ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87, the giant elliptical galaxy near the dynamical center of the Virgo Cluster. These images - with a total exposure time of 154 ks - are the deepest X-ray observations yet obtained of M87. We identify 174 X-ray point sources, of which 150 are likely LMXBs.
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- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/343/293
- Title:
- ELAIS deep X-ray survey. I.
- Short Name:
- J/MNRAS/343/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of two deep (75ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to two soft extended sources, which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources.
- ID:
- ivo://CDS.VizieR/J/AJ/127/213
- Title:
- LALA Bootes field X-ray source catalog
- Short Name:
- J/AJ/127/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of a deep, 172ks Chandra observation of the Large Area Lyman Alpha survey (LALA) Bootes field, obtained with the Advanced CCD Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This is one of the deepest Chandra images of the extragalactic sky; only the 2Ms Chandra Deep Field North (CDF-N) and 1Ms Chandra Deep Field South (CDF-S) are substantially deeper. In this paper we present the X-ray source catalog obtained from this image, along with an analysis of source counts and optical identifications. The X-ray image is composed of two individual observations obtained in 2002 and reaches 0.5-2.0 and 2.0-10.0keV flux limits of 1.5x10^-16^ and 1.0x10^-15^ergs/cm^2^/s, respectively, for point sources near the aim point. A total of 168 X-ray sources were detected: 160 in the 0.5-7.0keV band, 132 in the 0.5-2.0keV band, and 111 in the 2.0-7.0keV band. Our primary optical data are R-band imaging from the NOAO Deep Wide-Field Survey (NDWFS), with a limiting magnitude of R=25.7 (Vega, 3{sigma}, and 4" diameter aperture).
- ID:
- ivo://CDS.VizieR/J/ApJ/596/944
- Title:
- SEXSI catalog
- Short Name:
- J/ApJ/596/944
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Serendipitous Extragalactic X-Ray Source Identification (SEXSI) program is designed to extend greatly the sample of identified extragalactic hard X-ray (2-10keV) sources at intermediate fluxes (~10^-13^ to 10^-15^erg/cm^2^/s). SEXSI, which studies sources selected from more than 2deg^2^, provides an essential complement to the Chandra Deep Fields, which reach depths of 5x10^-16^erg/cm^2^/s (2-10keV) but over a total area of less than 0.2deg^2^. In this paper we describe the characteristics of the survey and our X-ray data analysis methodology. We present the cumulative flux distribution for the X-ray sample of 1034 hard sources and discuss the distribution of spectral hardness ratios. Our logN-logS in this intermediate flux range connects to those found in the Deep Fields, and by combining the data sets, we constrain the hard X-ray population over the flux range in which the differential number counts change slope and from which the bulk of the 2-10keV X-ray background arises. We further investigate the logN-logS distribution separately for soft and hard sources in our sample, finding that while a clear change in slope is seen for the softer sample, the hardest sources are well described by a single power law down to the faintest fluxes, consistent with the notion that they lie at lower average redshift.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2223
- Title:
- SPICES II: CHANDRA observations of Lynx
- Short Name:
- J/AJ/123/2223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our first results on field X-ray sources detected in a deep, 184.7ks observation with the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-Ray Observatory. The observations target the Lynx field (RA=08h48min, DE=+44{deg}54') of SPICES, the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey, which contains three known X-ray-emitting clusters at redshifts of z=0.57, 1.26, and 1.27. Not including the known clusters, in the 17'x17' ACIS-I field we detect 132 sources in the 0.5-2keV (soft) X-ray band down to a limiting flux of ~1.7x10^-16^ergs/cm^2^/s and 11 sources in the 2-10keV (hard) X-ray band down to a limiting flux of ~1.3x10^-15^ergs/cm^2^/s. The combined catalog contains a total of 153 sources, of which 42 are detected only in the soft band and 21 are detected only in the hard band. Confirming previous Chandra results, we find that the fainter sources have harder X-ray spectra, providing a consistent solution to the long-standing "spectral paradox." From deep optical and near-infrared follow-up data, 77% of the X-ray sources have optical counterparts to I=24, and 71% of the X-ray sources have near-infrared counterparts to Ks=20. Four of the 24 sources in the near-IR field are associated with extremely red objects (EROs; I-Ks>=4). We have obtained spectroscopic redshifts with the Keck telescopes of 18 of the Lynx Chandra sources. These sources comprise a mix of broad-lined active galaxies, apparently normal galaxies, and two late-type Galactic dwarfs. Intriguingly, one Galactic source is identified with an M7 dwarf exhibiting nontransient, hard X-ray emission. Thirteen of the Chandra sources are located within regions for which we have Hubble Space Telescope imaging. Nine of the sources are detected, showing a range of morphologies: several show compact cores embedded within diffuse emission, while others are spatially extended showing typical galaxy morphologies. Two of the Chandra sources in this subsample appear to be associated with mergers. We briefly review non-active galactic nucleus mechanisms to produce X-ray emission and discuss properties of the Lynx Chandra sample in relation to other samples of X-ray and non-X-ray sources.
- ID:
- ivo://CDS.VizieR/J/AJ/126/539
- Title:
- The Chandra Deep Fields North and South
- Short Name:
- J/AJ/126/539
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present point-source catalogs for the ~2Ms exposure of the Chandra Deep Field North, currently the deepest X-ray observation of the universe in the 0.5-8.0keV band. Five hundred and three (503) X-ray sources are detected over an ~448arcmin^2^ area in up to seven X-ray bands. Twenty (20) of these X-ray sources lie in the central 5.3 arcmin^2^ Hubble Deep Field North (13600^+3800^_-3000_sources/deg^2^). The on-axis sensitivity limits are 2.5x10^-17^ergs/cm^2^/s (0.5-2.0keV) and 1.4x10^-16^ergs/cm^2^/s (2-8keV). Source positions are determined using matched-filter and centroiding techniques; the median positional uncertainty is ~0.3". To allow consistent comparisons, the point-source catalogs for the 1Ms Chandra Deep Field South (CDF-S; see Cat. J/ApJS/139/369) have also been produced. Three hundred and twenty-six (326) X-ray sources are included in the main Chandra South catalog, and an additional 42 optically bright X-ray sources are included in a lower significance Chandra catalog. We find good agreement with the photometry of the previously published CDF-S catalogs; however, we provide significantly improved positional accuracy.
- ID:
- ivo://CDS.VizieR/IX/45
- Title:
- The Chandra Source Catalog, Release 1.1
- Short Name:
- IX/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public Advanced CCD Imaging Spectrometer imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <~30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1-{sigma} uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of <~1 false source per field for a 100ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a source is detected.
