The Spitzer mid-infrared AGN survey. II. The demographics and cosmic evolution of the AGN population

Journal Article · Wed Apr 01 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/802/2/102· OSTI ID:22882596

Lacy, M. ^[1]; Ridgway, S. E. ^[2]; Sajina, A. ^[3]; Petric, A. O. ^[4]; Gates, E. L. ^[5]; Urrutia, T. ^[6]

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1. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
2. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ, 85719 (United States)
3. Department of Physics and Astronomy, Tufts University, 212 College Avenue, Medford, MA 02155 (United States)
4. Gemini Observatory, Northern Operations Center, 670 N. A’ohoku Place, Hilo, HI 96720 (United States)
5. UCO/Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States)
6. Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482, Potsdam (Germany)

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 ∼10{sup 14} L{sub ⊙}. 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{sub −0.07}{sup +0.12} is required to match current estimates of the local mass density in black holes.

• OSTI ID: 22882596
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 802; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
BOLOMETERS
COMPARATIVE EVALUATIONS
COSMIC DUST
DENSITY
GALAXIES
GALAXY NUCLEI
HARD X RADIATION
LUMINOSITY
MASS
QUASARS
RED SHIFT
SPACE
TELESCOPES
UNIVERSE