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Published July 1, 2012 | Published
Journal Article Open

A Population of Dust-rich Quasars at z ~ 1.5


We report Herschel SPIRE (250, 350, and 500 μm) detections of 32 quasars with redshifts 0.5 ≤z < 3.6 from the Herschel Multi-tiered Extragalactic Survey (HerMES). These sources are from a MIPS 24 μm flux-limited sample of 326 quasars in the Lockman Hole Field. The extensive multi-wavelength data available in the field permit construction of the rest-frame spectral energy distributions (SEDs) from ultraviolet to the mid-infrared for all sources, and to the far-infrared (FIR) for the 32 objects. Most quasars with Herschel FIR detections show dust temperatures in the range of 25-60 K, with a mean of 34 K. The FIR luminosities range from 10^(11.3) to 10^(13.5) L_☉, qualifying most of their hosts as ultra- or hyper-luminous infrared galaxies. These FIR-detected quasars may represent a dust-rich population, but with lower redshifts and fainter luminosities than quasars observed at ~1 mm. However, their FIR properties cannot be predicted from shorter wavelengths (0.3-20 μm, rest frame), and the bolometric luminosities derived using the 5100 Å index may be underestimated for these FIR-detected quasars. Regardless of redshift, we observed a decline in the relative strength of FIR luminosities for quasars with higher near-infrared luminosities.

Additional Information

© 2012 The American Astronomical Society. Received 2011 August 11; accepted 2012 April 27; published 2012 June 12. This research has made use of data from the HerMES project—a Herschel Key Program utilizing Guaranteed Time from the SPIRE instrument team, ESAC scientists and a mission scientist. SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including the University of Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, the University of Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, the University of Sussex (UK); Caltech, JPL, NHSC, the University of Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC and UKSA (UK); and NASA (USA). The HerMES data were accessed through the HeDaM database (http://hedam.oamp.fr) operated by CeSAM and hosted by the Laboratoire d'Astrophysique de Marseille. We acknowledge support from the Science and Technology Facilities Council (grant numbers ST/F002858/1 and ST/I000976/1). This work is based partly on observations made with the Spitzer Space Telescope and the MMT Observatory, operated by the Jet Propulsion Laboratory, Caltech under a contract with NASA, the Smithsonian Astrophysical Observatory and the University of Arizona, respectively. Research by Y. S. D. is supported by the SAO Predoctoral Fellowship. Facilities: Herschel, MMT, Spitzer

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