X-ray surveys of the extragalactic universe are now able to detect significant numbers of AGN out to high redshift (z~5). We highlight some results from the Chandra Multiwavelength Project (ChaMP) to measure the X-ray luminosity function out to these early epochs. At z > 3, we show that the comoving space density of luminous (log Lx > 44.5) AGN has a behavior similar to the optical QSO luminosity function. With a newly compiled sample of AGN from ChaMP supplemented with those from additional surveys including the Chandra Deep fields, we present a preliminary measure of the luminosity function in the hard (2-8 keV) band. With 37 AGN at z > 3, we continue to see a decline in the space density at high redshift over a wider range in luminosity. We discuss the need to identify a larger sample of obscured AGN at high redshift to determine if an early epoch of hidden supermassive black hole growth occurred.
@article{arxiv.astro-ph/0511552,
title = {Extending the X-ray luminosity function of AGN to high redshift},
author = {J. Silverman and P. Green and W. Barkhouse and R. Cameron and M. Kim and D. -W. Kim and B. Wilkes and G. Hasinger and the full ChaMP team},
journal= {arXiv preprint arXiv:astro-ph/0511552},
year = {2007}
}
Comments
6 pages, 4 figures, to appear in Proc. "The X-ray Universe 2005", San Lorenzo de El Escorial, Spain, September 2005