The angular clustering of infrared-selected obscured and unobscured quasars

M. A. DiPompeo, A. D. Myers, R. C. Hickox, J. E. Geach, K. N. Hainline

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

Recent studies of luminous infrared-selected active galactic nuclei (AGN) suggest that the reddest, most obscured objects display a higher angular clustering amplitude, and thus reside in higher mass darkmatter haloes. This is a direct contradiction to the prediction of the simplest unification-by-orientation models of AGN and quasars. However, clustering measurements depend strongly on the 'mask' that removes low-quality data and describes the sky and selection function.We find that applying a robust, conservative mask to WISE-selected quasars yields a weaker but still significant difference in the bias between obscured and unobscured quasars. These findings are consistent with results from previous Spitzer surveys, and removes any scale dependence of the bias. For obscured quasars with <z> =0.99, we measure a bias of bq = 2.67 ± 0.16, corresponding to a halo mass of log(Mh/M⊙h-1) = 13.3 ± 0.1, while for unobscured sources with <z> = 1.04 we find bq = 2.04 ± 0.17 with a halo mass log(Mh/M⊙h-1) = 12.8 ± 0.1. This improved measurement indicates that WISE-selected obscured quasars reside in haloes only a few times more massive than the haloes of their unobscured counterparts, a reduction in the factor of ∼10 larger halo mass as has been previously reported using WISE-selected samples. Additionally, an abundance matching analysis yields lifetimes for both obscured and unobscured quasar phases on the order of a few 100 Myr (∼1 per cent of the Hubble time) - however, the obscured phase lasts roughly twice as long, in tension with many model predictions.

Original languageEnglish (US)
Pages (from-to)3443-3453
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume442
Issue number4
DOIs
StatePublished - Aug 2014
Externally publishedYes

Keywords

  • Evolution
  • Galaxies
  • Galaxies active
  • Quasars general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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