RICHARD MUSHOTZKY, GODDARD SPACE FLIGHT CENTER

PRINCETON ASTRONOMY COLLOQUIUM - FEBRUARY 1, 2005

ABSTRACT

The Accretion History of Massive Black Holes

We use highly spectroscopically complete deep and wide-area Chandra surveys to determine the cosmic evolution of hard X-ray-selected AGNs and determine hard X-ray luminosity functions. Our results are a revolution in AGN demography since we find that the number of, location of, evolution of and nature of AGN are very different from those found in pre- 2001 classical AGN surveys.

At z<1.2, both the luminosity functions are well described by pure luminosity evolution. On average AGNs drop in luminosity by almost an order of magnitude over this redshift range due to AGN downsizing. Contrary to optical surveys the energy density of AGN radiation drops at z>1.2. The areal density of all objects is ~7 times larger than in ‘classical’ color selected AGN surveys. The host galaxies of the x-ray selected objects at all redshifts tend to be drawn from the most luminous galaxies.

We directly compare our luminosity function of optical broad line objects with the optical QSO ones and find excellent agreement at high luminosities. BLAGNs dominate the number densities at the higher X-ray luminosities, while optically-narrow AGNs (FWHM<2000 km/s) dominate at the lower X-ray luminosities. We use the nuclear UV/optical properties of the Chandra sources from the HST ACS GOODS-North data to show that this effect is not due to galaxy dilution and only ~1/2 of the AGN nuclei are detected in the HST data. The UV/optical nuclei of the optically-narrow AGNs are much weaker than expected if they were similar to the BLAGNs.

We infer the bolometric corrections needed to map the accretion history of black holes. The accreted supermassive black hole mass density for all spectral types and for BLAGNs alone is obtained using the observed evolution of the hard X-ray energy density production rate and only ~1/4-1/2 of all the accretion energy is produced by optically color selected objects. The sum of the total mass for the x-ray selected objects is very close to the z=0 rest mass energy density of all black holes leaving little room for other sources of black hole mass.

We derive the 3-D correlation function of the x-ray selected objects in 4 redshift shells and compare it to the 2dF samples and despite the very different sample selection obtain similar results.