THE CHANDRA COSMOS SURVEY. III. OPTICAL AND INFRARED IDENTIFICATION OF X-RAY POINT SOURCES

By F. Civano, M. Elvis, M. Brusa, A. Comastri, Mara Salvato, G. Zamorani, Tom Aldcroft, A. Bongiorno, P. Capak, N. Cappelluti and 22 more. 2012

201 citations recorded by the source corpus.

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg2 of the COSMOS field down to limiting depths of 1.9 × 10−16 erg cm−2 s−1 in the soft (0.5–2 keV) band, 7.3 × 10−16 erg cm−2 s−1 in the hard (2–10 keV) band, and 5.7 × 10−16 erg cm−2 s−1 in the full (0.5–10 keV) band. In this paper we report the i, K, and 3.6 μm identifications of the 1761 X-ray point sources. We 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 we 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 online. Making use of the large number of X-ray sources, we update the “classic locus” of active galactic nuclei (AGNs) defined 20 years ago in soft X-ray surveys and define a new locus containing 90% of the AGNs in the survey with full-band luminosity >1042 erg s−1. We present the linear fit between the total i-band magnitude and the X-ray flux in the soft and hard bands, drawn over two orders of magnitude in X-ray flux, obtained using the combined C-COSMOS and XMM-COSMOS samples. We focus on the X-ray to optical flux ratio (X/O) and we test its known correlation with redshift and luminosity, and a recently introduced anti-correlation with the concentration index (C). We find a strong anti-correlation (though the dispersion is of the order of 0.5 dex) between X/O computed in the hard band and C and that 90% of the obscured AGNs in the sample with morphological information live in galaxies with regular morphology (bulgy and disky/spiral), suggesting that secular processes govern a significant fraction of the black hole growth at X-ray luminosities of 1043–1044.5 erg s−1. We also investigate the degree of obscuration of the sample using the hardness ratio, and we compare the X-ray color with the near-infrared to optical color.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ddcd11fadb19d9337b6ab901bc2a11b4d5a5cccf

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Citations in the corpus

Observational evidence for intermediate-mass black holes (2017, methodology): “Using a stacking analysis of early-type galaxies in the Chandra COSMOS survey (0.9 deg2, 1.8 Ms; Elvis et al. 2009; Civano et al. 2012) and after removing the contribution from XRBs and hot gas to the X-ray emission, Paggi et al. (2016) also found that highly absorbed AGN are present in low-mass…”
OBSCURATION-DEPENDENT EVOLUTION OF ACTIVE GALACTIC NUCLEI (2015, methodology): “Redshifts in the C-COSMOS are used from the compilation of Civano et al. (2012) which includes the public releases of the VIMOS/zCOSMOS bright project (Lilly et al. 2009) and the Magel- 5 lan/IMACS observation campaigns (Trump et al. 2009).”
BLACK HOLE VARIABILITY AND THE STAR FORMATION–ACTIVE GALACTIC NUCLEUS CONNECTION: DO ALL STAR-FORMING GALAXIES HOST AN ACTIVE GALACTIC NUCLEUS? (2013, background): “…Hickox et al. 2009; Coil et al. 2009; Donoso et al. 2010; Li et al. 2006) and morphologies (e.g., Cisternas et al. 2011; Schawinski et al. 2011; Civano et al. 2012; Kocevski et al. 2012) of moderate-luminosity AGNs are generally consistent with those for “normal” galaxies with similar mass,…”
Cosmic X-ray surveys of distant active galaxies (2015, methodology): “A few indepth applications of these methods include Alexander et al (2005a), Brusa et al (2010), Laird et al (2010), Xue et al (2011), Lehmer et al (2012), Civano et al (2012), and Wang et al (2013).”
Accreting supermassive black holes in the COSMOS field and the connection to their host galaxies (2012, background): “1 shows a graphical representation of the sample and its basic substructure, highlighting 3 We note here that seven of the 147 purely optically selected AGNs are actually detected in the deeper Chandra observation covering the central part of the COSMOS field (Elvis et al. 2009; Civano et al. 2012).”
THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS (2015, background): “…sources are also bright enough to obtain almost complete optical and near-infrared (near-IR) identifications of the X-ray sources (97% in C-COSMOS, Civano et al. 2012b, C12 hereafter): this extended follow-up is also due to the comprehensive nature of the Cosmic Evolutionary Survey (COSMOS;…”
The DEIMOS 10K Spectroscopic Survey Catalog of the COSMOS Field (2018, background): “15 http://www2.keck.hawaii.edu/inst/deimos/dsim.html and Chandra (e.g., Civano et al. 2012; Marchesi et al. 2016a, 2016b) surveys (PI: Hasinger); this is the “X-ray” subsample.”
THE KMOS3D SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ⩽ z ⩽ 2.7 (2014, background): “The fields further benefit from multi-wavelength coverage from the X-ray to far-IR and radio (e.g. Ueda et al. 2008; Lutz et al. 2011; Xue et al. 2011; Civano et al. 2012; Magnelli et al. 2013).”
A remarkably flat relationship between the average star formation rate and AGN luminosity for distant X-ray AGN. (2015, methodology): “To allocate the redshift counterpart of the sources in GOODS-S and C-COSMOS we make use of the spectroscopic and photometric redshift compilation by Xue et al. (2011) and Civano et al. (2012), respectively.”
THE CHANDRA COSMOS LEGACY SURVEY: OVERVIEW AND POINT SOURCE CATALOG (2016, methodology): “Indeed, the large (1.8 Ms) Chandra COSMOS survey (C-COSMOS; Elvis et al. 2009, E09; Puccetti et al. 2009, P09; Civano et al. 2012) has already contributed significantly to the study of the early epochs of the Universe, finding: three luminous AGN residing in protoclusters between z∼4.55 and 5.3…”
A statistical relation between the X-ray spectral index and Eddington ratio of active galactic nuclei in deep surveys (2013, methodology): “In the COSMOS survey, the targets of the FMOS observations were the optical counterparts of type 1 AGN detected in the Chandra– COSMOS survey (Elvis et al. 2009; Civano et al. 2012).”
THE COSMOS2015 CATALOG: EXPLORING THE 1 < z < 6 UNIVERSE WITH HALF A MILLION GALAXIES (2016, methodology): “In the catalog we also added the match with X-ray detected sources from XMM-COSMOS (Hasinger et al. 2007; Cappelluti et al. 2007; Brusa et al. 2010) and the previous Chandra COSMOS catalog (Elvis et al. 2009; Civano et al. 2012).”