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29 March 2024
 
  » arxiv » 1501.4118

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The Spitzer mid-infrared AGN survey. II-the demographics and cosmic evolution of the AGN population
Mark Lacy ; Susan E. Ridgway ; Anna Sajina ; Andreea O. Petric ; Elinor L. Gates ; Tanya Urrutia ; Lisa J. Storrie-Lombardi ;
Date 16 Jan 2015
AbstractWe present luminosity functions derived from a spectroscopic survey of AGN 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 the obscured and unobscured AGN 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 AGN at a given bolometric luminosity than found by either optical quasar surveys or hard X-ray surveys. The fraction of obscured AGN decreases rapidly with increasing AGN luminosity, but, at least at high redshifts, appears to remain at $approx 50$\% even at bolometric luminosities $sim 10^{14}L_{odot}$. 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 AGN contribute about 12\% to the total radiation intensity of the Universe, and a high radiative accretion efficiency $approx 0.18^{+0.12}_{-0.07}$ is required to match current estimates of the local mass density in black holes.
Source arXiv, 1501.4118
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