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29 March 2024 |
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Article overview
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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 | Abstract: | We 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 | Services: | Forum | Review | PDF | Favorites |
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