The Chandra COSMOS Legacy survey: optical/IR identifications

Journal
Date Issued
2016
Author(s)
•
Civano, F.
•
Elvis, M.
•
Salvato, M.
•
Brusa, M.
•
•
•
Hasinger, G.
•
•
Miyaji, T.
•
Treister, E.
•
Urry, C. M.
•
Vignali, C.
•
Zamorani, G.
•
•
Cappelluti, N.
•
Cardamone, C.
•
Finoguenov, A.
•
Griffiths, R. E.
•
Karim, A.
•
Laigle, C.
•
LaMassa, S. M.
•
Jahnke, K.
•
Ranalli, P.
•
Schawinski, K.
•
Schinnerer, E.
•
Silverman, J. D.
•
Smolcic, V.
•
Suh, H.
•
Trakhtenbrot, B.
DOI
Abstract
We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 deg2 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 μm 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 μm 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 2-10 keV 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.
Volume
817
Issue
1
Start page
34
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...817...34M
Rights
open.access
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