Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars

Creators: Richards, Gordon T.; Lacy, Mark; Storrie-Lombardi, Lisa J.; Hall, Patrick B.; Gallagher, S. C.; Hines, Dean C.; Fan, Xiaohui; Papovich, Casey; Vanden Berk, Daniel E.; Trammell, George B.; Schneider, Donald P.; Vestergaard, Marianne; York, Donald G.; Jester, Sebastian; Anderson, Scott F.; Budavári, Tamás; Szalay, Alexander S.

Abstract

We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z ~ 3, with predictions to z = 7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as 50% for individual quasars when inferring a bolometric luminosity from an optical luminosity. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio.

Additional Information

© 2006 American Astronomical Society. Received 2006 January 24; accepted 2006 May 26. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, Cambridge University, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPA), the Max-Planck-Institute for Astrophysics (MPIA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. This work is based on observations made with the Spitzer Space Telescope, operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with NASA. Support was provided by NASA through JPL. G. T. R. further acknowledges support from a Gordon and Betty Moore Fellowship in data intensive sciences. X. F. and M. V. acknowledge support from NSF grant AST-0307384.We thank an anonymous referee, especially for helping with figure presentation and also Eilat Glikman for making her IR quasar composite spectrum available in advance of publication.

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