2015ApJ...802..102L

We present luminosity functions derived from a spectroscopic survey of active galactic nuclei (AGNs) selected from Spitzer Space Telescope imaging surveys. Selection in the mid-infrared is significantly less affected by dust obscuration. We can thus compare the luminosity functions of obscured and unobscured AGNs in a more reliable fashion than by using optical or X-ray data alone. We find that the AGN luminosity function can be well described by a broken power-law model in which the break luminosity decreases with redshift. At high redshifts (z > 1.6), we find significantly more AGNs at a given bolometric luminosity than found by either optical quasar surveys or hard X-ray surveys. The fraction of obscured AGNs decreases rapidly with increasing AGN luminosity, but, at least at high redshifts, appears to remain at ≈50% even at bolometric luminosities ∼10¹⁴L_☉. The data support a picture in which the obscured and unobscured populations evolve differently, with some evidence that high luminosity obscured quasars peak in space density at a higher redshift than their unobscured counterparts. The amount of accretion energy in the universe estimated from this work suggests that AGNs contribute about 12% to the total radiation intensity of the universe, and a high radiative accretion efficiency ≈0.18_–0.07^+0.12 is required to match current estimates of the local mass density in black holes.