The Spitzer Mid-infrared AGN Survey. II. The Demographics and Cosmic Evolution of the AGN Population
Abstract
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^(14)L_☉. 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.
Additional Information
© 2015 American Astronomical Society. Received 2014 February 8; accepted 2015 January 16; published 2015 March 30. We thank the referee whose comments significantly improved the paper. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.Attached Files
Published - 0004-637X_802_2_102.pdf
Submitted - 1501.04118v1.pdf
Files
Name | Size | Download all |
---|---|---|
md5:eedf967af0422be97a44d043833eacf2
|
434.2 kB | Preview Download |
md5:2e34aed181e4452e433d2edc30ab7e5c
|
1.5 MB | Preview Download |
Additional details
- Eprint ID
- 53975
- Resolver ID
- CaltechAUTHORS:20150122-083732911
- NSF
- Associated Universities, Inc.
- Created
-
2015-01-22Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)