Lifting the Veil of Distant Compton-thick AGNs

David Alexander, Durham University

Many models that seek to explain the origin of the unresolved X-ray background predict that Compton-thick AGNs are ubiquitous at high redshift. However, due to their faintness at X-ray energies, Compton-thick AGNs are notoriously difficult to identify, even in the deepest X-ray surveys currently available. I will present the most recent results on the identification of candidate Compton-thick AGNs at z~2 from photometric data and I will then show how distant Compton-thick AGNs can be reliably found when spectroscopic observations are included. I will discuss the properties of these distant Compton-thick AGNs, including constraints on their space density, energetics, and contribution to the growth of massive black holes.