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Start Over Subject infrared photometry Subject redshifted Subject x-ray sources
1. A complete sample of broad-line AGN from SDSS-DR7
ID:
ivo://CDS.VizieR/J/ApJS/243/21
Title:
A complete sample of broad-line AGN from SDSS-DR7
Short Name:
J/ApJS/243/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new, complete sample of 14584 broad-line active galactic nuclei (AGNs) at z<0.35 is presented, which are uncovered homogeneously from the complete database of galaxies and quasars observed spectroscopically in the Sloan Digital Sky Survey Seventh Data Release. The stellar continuum is properly removed for each spectrum with significant host absorption line features, and careful analyses of the emission line spectra, particularly in the H{alpha} and H{beta} wavebands, are carried out. The broad Balmer emission line, particularly H{alpha}, is used to indicate the presence of an AGN. The broad H{alpha} lines have luminosities in a range of 10^38.5^-10^44.3^erg/s, and line widths (FWHMs) of 500-34000km/s. The virial black hole masses, estimated from the broad-line measurements, span a range of 10^5.1^-10^10.3^M_{sun}_, and the Eddington ratios vary from -3.3 to 1.3 in logarithmic scale. Other quantities such as multiwavelength photometric properties and flags denoting peculiar line profiles are also included in this catalog. We describe the construction of this catalog and briefly discuss its properties. The catalog is publicly available online. This homogeneously selected AGN catalog, along with the accurately measured spectral parameters, provides the most updated, largest AGN sample data, which will enable further comprehensive investigations of the properties of the AGN population in the low-redshift universe.
2. AEGIS-X Deep survey of EGS (AEGIS-XD)
ID:
ivo://CDS.VizieR/J/ApJS/220/10
Title:
AEGIS-X Deep survey of EGS (AEGIS-XD)
Short Name:
J/ApJS/220/10
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of deep Chandra imaging of the central region of the Extended Groth Strip, the AEGIS-X Deep (AEGIS-XD) survey. When combined with previous Chandra observations of a wider area of the strip, AEGIS-X Wide (AEGIS-XW), these provide data to a nominal exposure depth of 800ks in the three central ACIS-I fields, a region of approximately 0.29deg^2^. This is currently the third deepest X-ray survey in existence; a factor ~2-3 shallower than the Chandra Deep Fields (CDFs), but over an area ~3 times greater than each CDF. We present a catalog of 937 point sources detected in the deep Chandra observations, along with identifications of our X-ray sources from deep ground-based, Spitzer, GALEX, and Hubble Space Telescope imaging. Using a likelihood ratio analysis, we associate multiband counterparts for 929/937 of our X-ray sources, with an estimated 95% reliability, making the identification completeness approximately 94% in a statistical sense. Reliable spectroscopic redshifts for 353 of our X-ray sources are available predominantly from Keck (DEEP2/3) and MMT Hectospec, so the current spectroscopic completeness is ~38%. For the remainder of the X-ray sources, we compute photometric redshifts based on multiband photometry in up to 35 bands from the UV to mid-IR. Particular attention is given to the fact that the vast majority the X-ray sources are active galactic nuclei and require hybrid templates. Our photometric redshifts have mean accuracy of {sigma}=0.04 and an outlier fraction of approximately 5%, reaching {sigma}=0.03 with less than 4% outliers in the area covered by CANDELS.
3. AGN candidates from the WISE, 2MASS, RASS (W2R)
ID:
ivo://CDS.VizieR/J/ApJ/751/52
Title:
AGN candidates from the WISE, 2MASS, RASS (W2R)
Short Name:
J/ApJ/751/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have developed the "S_IX_" statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3m Kast spectroscopy. We find that sources with S_IX_<0 have a >~95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the "W2R" sample of 4316 sources with S_IX_<0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J<~16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J<14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg^2^, permitting construction of AGN samples in any sufficiently large region of sky.
4. BL Lac candidates for TeV observations
ID:
ivo://CDS.VizieR/J/ApJS/207/16
Title:
BL Lac candidates for TeV observations
Short Name:
J/ApJS/207/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
BL Lac objects are the most numerous class of extragalactic TeV-detected sources. One of the biggest difficulties in investigating their TeV emission is due to their limited number, since only 47 BL Lac objects are known to be TeV emitters. In this paper, we propose new criteria to select TeV BL Lac candidates based on infrared and X-ray observations. We apply our selection criteria to the BL Lac objects listed in the ROMA-BZCAT catalog (Cat. J/A+A/495/691), thereby identifying 41 potential TeV emitters. We then perform a search over a more extended sample combining the ROSAT bright source catalog (Cat. IX/10) and the WISE all-sky survey (Cat. II/311), revealing 54 additional candidates for TeV observations. Our investigation also led to a tentative classification of 16 unidentified X-ray sources as BL Lac candidates. This analysis provides new interesting BL Lac targets for future observations with ground-based Cherenkov telescopes.
5. Catalog of X-ray selected BL Lac objects
ID:
ivo://CDS.VizieR/J/AJ/145/31
Title:
Catalog of X-ray selected BL Lac objects
Short Name:
J/AJ/145/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents a catalog of 312 X-ray selected BL Lacertae objects (XBLs), optically identified through the end of 2011. It contains the names from different surveys, equatorial coordinates, redshifts, multifrequency flux values, and luminosities for each source. In addition, the different characteristics of XBLs are statistically investigated (redshift, radio/optical/X-ray luminosities, central black hole (BH) mass, synchrotron peak frequency, broadband spectral indices, optical flux variability). Their values are collected through an extensive bibliographic and database search or calculated by us. The redshifts range from 0.031 to 0.702 with a maximum of the distribution at z=0.223. The 1.4GHz luminosities of XBLs log{nu}L_{nu}_~39-42erg/s while optical V and X-ray 0.1-2.4keV bands show log{nu}L_{nu}_~43-46erg/s. The XBL hosts are elliptical galaxies with effective radii r_eff_=3.26-25.40kpc and ellipticities, {epsilon}=0.04-0.52. Their R-band absolute magnitudes M_R_ range from -21.11mag to -24.86mag with a mean value of -22.83mag. The V-R indices of the hosts span from 0.61 to 1.52 and reveal a fourth-degree polynomial relationship with z that enables us to evaluate the redshifts of five sources whose V-R indices were determined from the observations but whose redshifts values are either not found or not confirmed. The XBL nuclei show a wider range of 7.31mag for M_R_ with the highest luminosity corresponding to M_R_=-27.24mag. The masses of central BHs are found in the interval logM_BH_=7.39-9.30 solar masses (with distribution maximum at logM_BH_/M_{sun}_=8.30). The synchrotron peak frequencies are spread over the range log{nu}_peak_=14.56-19.18Hz with a peak of the distribution at log{nu}_peak_=16.60Hz. The broadband radio-to-optical ({alpha}_ro_), optical-to-X-ray ({alpha}_ox_), and radio-to-X-ray ({alpha}_rx_) spectral indices are distributed in the intervals (0.17,0.59), (0.56,1.48), and (0.41,0.75), respectively. In the optical energy range, the overall flux variability increases, on average, towards shorter wavelengths: <{Delta}m>=1.22,1.50, and 1.82mag through the R, V, B bands of Johnson-Cousins system, respectively. XBLs seem be optically less variable at the intranight timescales compared to the radio-selected BL Lacs (RBLs).
6. C-COSMOS Legacy sources multiwavelength catalog
ID:
ivo://CDS.VizieR/J/ApJ/817/34
Title:
C-COSMOS Legacy sources multiwavelength catalog
Short Name:
J/ApJ/817/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6Ms Chandra program on the 2.2deg^2^ of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6{mu}m identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6{mu}m information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ~54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2-10keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.
7. CDWFS: Chandra survey in Bootes. I. X-ray cat.
ID:
ivo://CDS.VizieR/J/ApJS/251/2
Title:
CDWFS: Chandra survey in Bootes. I. X-ray cat.
Short Name:
J/ApJS/251/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new, ambitious survey performed with the Chandra X-ray Observatory of the 9.3deg^2^ Bootes field of the NOAO Deep Wide-Field Survey. The wide field probes a statistically representative volume of the universe at high redshift. The Chandra Deep Wide-field Survey exploits the excellent sensitivity and angular resolution of Chandra over a wide area, combining 281 observations spanning 15yr, for a total exposure time of 3.4Ms, and detects 6891 X-ray point sources down to limiting fluxes of 4.7x10^-16^, 1.5x10^-16^, and 9x10^-16^erg/cm^2^/s in the 0.5-7, 0.5-2, and 2-7keV bands, respectively. The robustness and reliability of the detection strategy are validated through extensive, state-of-the-art simulations of the whole field. Accurate number counts, in good agreement with previous X-ray surveys, are derived thanks to the uniquely large number of point sources detected, which resolve 65.0%+/-12.8% of the cosmic X-ray background between 0.5 and 2keV and 81.0%+/-11.5% between 2 and 7keV. Exploiting the wealth of multiwavelength data available on the field, we assign redshifts to ~94% of the X-ray sources, estimate their obscuration, and derive absorption-corrected luminosities.
8. 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^).
9. Color-magnitude relations of galaxies in CDFs
ID:
ivo://CDS.VizieR/J/ApJ/720/368
Title:
Color-magnitude relations of galaxies in CDFs
Short Name:
J/ApJ/720/368
Date:
21 Oct 2021
Publisher:
CDS
Description:
We extend color-magnitude relations for moderate-luminosity X-ray active galactic nucleus (AGN) hosts and non-AGN galaxies through the galaxy formation epoch (z~1-4) in the Chandra Deep Field-North and Chandra Deep Field-South (CDF-N and CDF-S, respectively; jointly CDFs) surveys. This study was enabled by the deepest available X-ray data from the 2Ms CDF surveys as well as complementary ultradeep multiwavelength data in these regions. We utilized analyses of color-magnitude diagrams (CMDs) to assess the role of moderate-luminosity AGNs in galaxy evolution.
10. Counterparts to 1.4GHz sources in ECDF-S
ID:
ivo://CDS.VizieR/J/ApJS/203/15
Title:
Counterparts to 1.4GHz sources in ECDF-S
Short Name:
J/ApJS/203/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study a sample of 883 sources detected in a deep Very Large Array survey at 1.4GHz in the Extended Chandra Deep Field South. This paper focuses on the identification of their optical and infrared (IR) counterparts. We use a likelihood-ratio technique that is particularly useful when dealing with deep optical images to minimize the number of spurious associations. We find a reliable counterpart for 95% of our radio sources. Most of the counterparts (74%) are detected at optical wavelengths, but there is a significant fraction (21%) that are only detectable in the IR. Combining newly acquired optical spectra with data from the literature, we are able to assign a redshift to 81% of the identified radio sources (37% spectroscopic). We also investigate the X-ray properties of the radio sources using the Chandra 4Ms and 250ks observations. In particular, we use a stacking technique to derive the average properties of radio objects undetected in the Chandra images. The results of our analysis are collected in a new catalog containing the position of the optical/IR counterpart, the redshift information, and the X-ray fluxes. It is the deepest multi-wavelength catalog of radio sources, which will be used for future study of this galaxy population.

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