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Powerful obscured AGN among X-ray hard, optically-dim serendipitous Chandra sources | | P. Gandhi
; C. S. Crawford
; A. C. Fabian
; R. M. Johnstone
; | | Date: |
27 Oct 2003 | | Journal: | Mon.Not.Roy.Astron.Soc. 348 (2004) 529 | | Subject: | astro-ph | | Affiliation: | 1,2), C. S. Crawford , A. C. Fabian and R. M. Johnstone ( ESO Chile, IoA Cambridge | | Abstract: | We present a small sample of Chandra X-ray sources selected from the fields of ACIS observations which probe fluxes around the break in the hard band source counts. The targets of these fields include 9 nearby galaxy clusters, 1 distant cluster and 2 powerful radio galaxy fields. The follow-up of this serendipitous sample was biased towards X-ray hard and optically-dim sources mostly not seen on the Digitized Sky Survey; for these, we present X-ray fluxes, optical and near-infrared photometry leading to 51 photometric redshifts in all and 18 independently measured spectroscopic redshifts. Few sources are associated with the target fields themselves. Fifty-six of 58 sources imaged in the K-band are detected at K<~20 with K_median=18, and of these, 38 have hard X-ray count ratios and 24 of these are significantly hard with most of the counts emerging about 2 keV. We find that almost all are AGN hosted in massive early-type host galaxies with a photometric redshift distribution peaking at z~1. Two type 2 quasars with intrinsic X-ray luminosity L>~10^{45} erg/s, Fe K_alpha emission lines and absorbing column density nH>10^{23} cm^{-2} -- and nH>~10^{24} cm^{-2} in one case -- are discussed in detail; the sample contains at least 12 potential type 2 quasars in all. We discuss various detection strategies for type 2 quasars and calculate their inferred space density. This combines and extends a number of results from subsamples already published by us. | | Source: | arXiv, astro-ph/0310772 | | Services: | Forum | Review | PDF | Favorites | |
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