The Population of High Redshift AGNs in the Chandra COSMOS survey
Abstract
We present the high redshift (3<z<5.3) 0.5-2 keV number counts and the 2-10 keV (rest frame) space density of X-ray selected AGNs detected in the Chandra COSMOS survey. The sample comprises 81 X-ray detected sources with available spectroscopic (31) and photometric (50) redshifts plus 20 sources with a formal z_phot<3 but with a broad photometric redshift probability distribution, such that z_phot+1sigma>3. 81 sources are selected in the 0.5-2 keV band, 14 are selected in the 2-10 keV and 6 in the 0.5-10 keV bands. We sample the high luminosity (log L_(2-10 keV)>44.15 erg/s) space density up to z~5 and a fainter luminosity range (43.5<log L(2-10 keV)<44.15 erg/s) than previous studies, up to z=3.5. We weighted the contribution to the number counts and the space density of the sources with photometric redshift by using their probability of being at z>3. We find that the space density of high-luminosity AGNs declines exponentially at all the redshifts, confirming the trend observed for optically selected quasars. At lower luminosity, the measured space density is not conclusive, and a larger sample of faint sources is needed. Comparisons with optical luminosity functions and BH formation models are presented together with prospects for future surveys.
Keywords
Cite
@article{arxiv.1103.2570,
title = {The Population of High Redshift AGNs in the Chandra COSMOS survey},
author = {F. Civano and M. Brusa and A. Comastri and M. Elvis and M. Salvato and G. Zamorani and P. Capak and F. Fiore and R. Gilli and H. Hao and H. Ikeda and Y. Kakazu and J. S. Kartaltepe and D. Masters and T. Miyaji and M. Mignoli and S. Puccetti and F. Shankar and J. Silverman and C. Vignali and A. Zezas and A. M. Koekemoer},
journal= {arXiv preprint arXiv:1103.2570},
year = {2015}
}
Comments
10 pages, 6 figures. ApJ in press. Table 3 is available in the published version