Spitzer Reveals Hidden Quasar Nuclei in Some Powerful FR II Radio Galaxies

We present a Spitzer mid-infrared survey of 42 Fanaroff-Riley class II radio galaxies and quasars from the 3CRR catalog at redshift z < 1. All of the quasars and 45% c 12% of the narrow-line radio galaxies have a mid-IR luminosity of uL sub(u)(15 km) > 8 x 10 super(43) ergs s super(-1), indica...

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Bibliographic Details
Published in:The Astrophysical journal 2006-08, Vol.647 (1), p.161-171
Main Authors: Ogle, Patrick, Whysong, David, Antonucci, Robert
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
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Summary:We present a Spitzer mid-infrared survey of 42 Fanaroff-Riley class II radio galaxies and quasars from the 3CRR catalog at redshift z < 1. All of the quasars and 45% c 12% of the narrow-line radio galaxies have a mid-IR luminosity of uL sub(u)(15 km) > 8 x 10 super(43) ergs s super(-1), indicating strong thermal emission from hot dust in the active galactic nucleus. Our results demonstrate the power of Spitzer to unveil dust-obscured quasars. The ratio of "mid-IR luminous" narrow-line radio galaxies to quasars indicates a mean dust covering fraction of 0.56 c 0.15, assuming relatively isotropic emission. We analyze Spitzer spectra of the 14 mid-IR luminous narrow-line radio galaxies thought to host hidden quasar nuclei. Dust temperatures of 210-660 K are estimated from single-temperature blackbody fits to the low- and high-frequency ends of the mid-IR bump. Most of the mid-IR luminous radio galaxies have a 9.7 km silicate absorption trough with optical depth
ISSN:0004-637X
1538-4357
DOI:10.1086/505337