Very High Redshift X-ray Selected Agn in the Chandra Deep Field-north

Deep Chandra X-ray exposures provide an efficient route for locating optically faint active galactic nuclei (AGN) at high redshifts. We use deep multicolor optical data to search for z > 5 AGN in the 2 Ms X-ray exposure of the Chandra Deep Field-North. Of the 423 X-ray sources bright enough (z < 25.2) for a color-color analysis, at most one lies at z = 5 − 6 and none at z > 6. The z > 5 object is spectroscopically confirmed at z = 5.19. Only 31 of the 77 sources with z > 25.2 are undetected in the B or V bands at the 2σ level and could lie at z > 5. There are too few moderate luminosity AGN at z = 5− 6.5 to ionize the intergalactic medium. Subject headings: cosmology: observations — galaxies: active — galaxies: evolution — galaxies: formation — galaxies: distances and redshifts