The 1 < z < 5 infrared luminosity function of type I quasars

Michael J.I. Brown, Kate Brand, Arjun Dey, Buell T. Jannuzi, Richard Cool, Emeric Le Floc'h, Christopher S. Kochanek, Lee Armus, Chao Bian, Jim Higdon, Sarah Higdon, Casey Papovich, George Rieke, Marcia Rieke, J. D. Smith, B. T. Soifer, Dan Weedman

Research output: Contribution to journalArticlepeer-review

72 Scopus citations


We determine the rest-frame 8 μm luminosity function of type I quasars over the redshift range 1 < z < 5. Our sample consists of 292 24 μm sources brighter than 1 mJy selected from 7.17 deg2 of the Spitzer Space Telescope MIPS survey of the NOAO Deep Wide-Field Survey Bootes field. The AGN and Galaxy Evolution Survey (AGES) has measured redshifts for 270 of the R < 21.7 sources, and we estimate that the contamination of the remaining 22 sources by stars and galaxies is low. We are able to select quasars missed by ultraviolet excess quasar surveys, including reddened type I quasars and 2.2 < z < 3.0 quasars with optical colors similar to main-sequence stars. We find that reddened type I quasars comprise ∼20% of the type I quasar population. Nonetheless, the shape, normalization, and evolution of the rest-frame 8 μm luminosity function are comparable to those of quasars selected from optical surveys. The 8 μm luminosity function of type I quasars is well approximated by a power law with index -2.75 ± 0.14. We directly measure the peak of the quasar space density to be at z = 2.6 ± 0.3.

Original languageEnglish (US)
Pages (from-to)88-99
Number of pages12
JournalAstrophysical Journal
Issue number1 I
StatePublished - Feb 10 2006


  • Quasars: general
  • Surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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