Optically faint sources in the Chandra Deep Field North Survey

D.M. Alexander (The Pennsylvania State University) and the Chandra Deep Field North Team

Abstract

A considerable fraction ($\approx$ 30%) of the sources that comprise the 0.5-8.0 keV X-ray background have optically faint ($I\ge24$) counterparts. Here we present constraints on the nature of this source population using the 1 Ms Chandra Deep Field North observation. We find that the majority of the optically faint sources are likely to be obscured AGN at moderate redshift ($z\approx$ 1-3), and a considerable fraction (10-50%) are probably obscured QSOs. Although these sources contribute to a significant fraction of the X-ray background radiation, we find that they are unlikely to be strong contributors to the far-infrared background. A number of sources have faint $\mu$Jy radio counterparts, and we place constraints on the nature of the optically faint $\mu$Jy source population.

CATEGORY: ACTIVE GALAXIES AND QUASARS