The Chandra COSMOS Legacy survey: optical/IR identifications

Marchesi, S. and Civano, F. and Elvis, M. and Salvato, M. and Brusa, M. and Comastri, A. and Gilli, R. and Hasinger, G. and Lanzuisi, G. and Miyaji, T. and Treister, E. and Urry, C. M. and Vignali, C. and Zamorani, G. and Allevato, V. and Cappelluti, N. and Cardamone, C. and Finoguenov, A. and Griffiths, R. E. and Karim, A. and Laigle, C. and LaMassa, S. M. and Jahnke, K. and Ranalli, P. and Schawinski, K. and Schinnerer, E. and Silverman, J. D. and Smolčić, Vernesa and Suh, H. and Trakhtenbrot, B. (2016) The Chandra COSMOS Legacy survey: optical/IR identifications. Astrophysical Journal, 817 (1). pp. 34-56. ISSN 0004-637X

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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.

Item Type: Article
Keywords: catalogs – cosmology: observations – galaxies: active – galaxies: evolution – surveys – X-rays: general
Date: 20 January 2016
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2016. The American Astronomical Society. All rights reserved. Received 2015 October 12; accepted 2015 November 30; published 2016 January 20.
Divisions: Faculty of Science > Department of Physics
Publisher: IOP Publishing
Depositing User: Vernesa Smolčić
Date Deposited: 09 May 2016 19:18
Last Modified: 29 Nov 2017 17:16

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