ar X iv : a st ro - p h / 05 11 55 2 v 1 1 8 N ov 2 00 5 1 EXTENDING THE X - RAY LUMINOSITY FUNCTION OF AGN TO HIGH REDSHIFT

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 L X > 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 luminos-ity 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.