The Accretion History of the Universe

Richard Mushotzky

The Chandra data on the sources of the X-ray background have provided fundamentally new information on where, when and how many radiating massive black holes there are in the Universe. Roughly 2/3 of all Chandra selected AGN are not found in optical surveys, while the Chandra observations find virtually all optically selected AGN. The Chandra sources have a different redshift evolution than optically selected AGN peaking at z~1 rather than z~2.5. They show strong luminosity evolution at z<1 and negative evolution at higher z. The host galaxies are luminous and red, probably mostly giant E galaxies at all redshifts. The Chandra sources also trace large scale structure in a manner indicating that they are highly biased tracers of structure.