The Chandra COSMOS Survey: III. Optical and Infrared Identification of X-ray Point Sources
Autor: | Civano, F., Elvis, M., Brusa, M., Comastri, A., Salvato, M., Zamorani, G., Aldcroft, T., Bongiorno, A., Capak, P., Cappelluti, N., Cisternas, M., Fiore, F., Fruscione, A., Hao, H., Kartaltepe, J., Koekemoer, A., Gilli, R., Impey, C. D., Lanzuisi, G., Lusso, E., Mainieri, V., Miyaji, T., Lilly, S., Masters, D., Puccetti, S., Schawinski, K., Scoville, N. Z., Silverman, J., Trump, J., Urry, M., Vignali, C., Wright, N. J. |
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Rok vydání: | 2012 |
Předmět: | |
Druh dokumentu: | Working Paper |
DOI: | 10.1088/0067-0049/201/2/30 |
Popis: | The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg^2 of the COSMOS field down to limiting depths of 1.9 10^-16 erg cm^-2 s-1 in the 0.5-2 keV band, 7.3 10^-16 erg cm^-2 s^-1 in the 2-10 keV band, and 5.7 10^-16 erg cm^-2 s-1 in the 0.5-10 keV band. In this paper we report the i, K and 3.6micron 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 2 sources are truly empty fields. Making use of the large number of X-ray sources, we update the "classic locus" of AGN and define a new locus containing 90% of the AGN in the survey with full band luminosity >10^42 erg/s. We present the linear fit between the total i band magnitude and the X-ray flux in the soft and hard band, drawn over 2 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 C and X/O, computed in the hard band, and that 90% of the obscured AGN 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 BH growth at X-ray luminosities of 10^43- 10^44.5 erg/s. Comment: 21 pages, 17 figures, 4 tables; accepted for publication in ApJS. The catalog is available at the urls listed in the paper |
Databáze: | arXiv |
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