%0 Journal Article
%T Detecting high redshift evolved galaxies as the hosts of optically faint hard X-ray sources
%A L. L. Cowie
%A A. J. Barger
%A M. W. Bautz
%A P. Capak
%A C. S. Crawford
%A A. C. Fabian
%A E. M. Hu
%A F. Iwamuro
%A J. -P. Kneib
%A T. Maihara
%A K. Motohara
%J Physics
%D 2001
%I arXiv
%R 10.1086/319839
%X We combine deep Subaru near-infrared images of the massive lensing clusters A2390 and A370 with Keck optical data to map the spectral energy distributions (SEDs) of Chandra X-ray sources lying behind the clusters. The three sources behind A2390 are found to have extremely red colors with SEDs consistent with evolved galaxies at redshifts z>1.4. One source has extremely anomalous colors, which we interpret as evidence for a type Sa SED at a redshift around 2.5. The photometric redshift of another source has been confirmed at z=1.467 from near-infrared spectroscopy using the CISCO spectrograph on Subaru. Mapping of optically faint hard X-ray sources may prove to be an extremely efficient way to locate luminous evolved galaxies at high redshifts.
%U http://arxiv.org/abs/astro-ph/0102306v1