Radio galaxies and type-2 quasars in the Spitzer Extragalactic First Look Survey
✍ Scribed by M. Lacy; A. Sajina; E. Gates; the XFLS Team
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 625 KB
- Volume
- 327
- Category
- Article
- ISSN
- 0004-6337
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✦ Synopsis
Abstract
We use mid‐infrared colour‐colour plots made with data from the Spitzer First Look Survey to explore the emission mechanisms of faint radio sources in that field. Using mid‐infrared colours alone, we are able to see the transition from a starburst‐dominated radio source population at sub‐mJy levels to the radiogalaxy/quasar population at mJy levels. Both FR I and some FR II galaxies show little or no mid‐infrared excess, suggesting they either lack dusty tori, or a strong continuum source to heat them, or both. Objects with hot, dusty tori, most likely radio‐intermediate and radio‐quiet AGN, make up a significant fraction of the faint radio source population. We also discuss the use of mid‐infrared colour‐colour plots to select radio quiet obscured AGN. Early results from imaging the host galaxies of these type‐2 quasars at high spatial resolution with adaptive optics indicates that they, like type‐1 quasars and radio galaxies, are often found to be hosted by giant elliptical galaxies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)