Andreas SCHULZE
(NAOJ)
Understanding the influence of black hole growth on galaxy evolution over cosmic time scales requires a census of the AGN population, in particular in respect to their black hole masses and accretion rates. These are traced by the cosmological evolution of the active black hole mass function and the Eddington ratio distribution function. We present new constraints on these distribution functions at z~4, beyond the peak of AGN and star formation activity, by combining SDSS with a deep AGN sample from COSMOS. These provide insight in the physical drivers of the AGN downsizing behavior in the AGN luminosity function and provide constraints on the early growth history of the supermassive black hole population.