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An Investigation into the Effects of Luminosity on the Mid-Infrared Spectral Energy Distributions of Radio-quiet Quasars

Gallagher, S. C. and Richards, G. T. and Lacy, M. and Hines, D. C. and Elitzur, M. and Storrie-Lombardi, L. J. (2007) An Investigation into the Effects of Luminosity on the Mid-Infrared Spectral Energy Distributions of Radio-quiet Quasars. Astrophysical Journal, 661 (1). pp. 30-37. ISSN 0004-637X. doi:10.1086/513733.

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We present an analysis of the effects of luminosity on the shape of the mid-infrared spectral energy distributions (SEDs) of 234 radio-quiet quasars originally presented by Richards et al. In quasars without evident dust extinction, the spectrally integrated optical and infrared luminosities are linearly correlated over nearly three decades in luminosity. We find a significant (≳99.99% confidence) correlation between the 1.8-8.0 μm spectral index and infrared luminosity that indicates an enhancement of the mid-infrared continuum with increasing luminosity. Coupled with strong evidence for spectral curvature in more luminous quasars, we conclude that this trend is likely a manifestation of the "near-infrared (3-5 μm) bump" noted in earlier quasar SED surveys. The strength of this feature is indicative of the contribution of emission from the hottest (≳1000 K) dust to the mid-infrared spectrum; higher luminosity quasars tend to show more hot dust emission. Finally, the comparable distribution of bolometric corrections from the monochromatic 3 μm luminosity as well as its lack of sensitivity to dust extinction as compared to the standard bolometric correction from νL_(5100 Å) suggest that the former may be a more robust indicator of bolometric quasar luminosity. The close link between the power in the mid-infrared and optical and the effect of luminosity on the shape of the mid-infrared continuum indicate that considering mid-infrared emission independent of the properties of the quasar itself is inadequate for understanding the parsec-scale quasar environment.

Item Type:Article
Related URLs:
URLURL TypeDescription
Lacy, M.0000-0002-3032-1783
Hines, D. C.0000-0003-4653-6161
Elitzur, M.0000-0001-8143-3550
Storrie-Lombardi, L. J.0000-0002-5987-5210
Additional Information:© 2007 American Astronomical Society. Received 2006 August 28; accepted 2007 February 9. We thank Maia Nenkova, Matt Malkan, and Bev Wills for sharing their expertise. Support for S. C. G. was provided by NASA through the Spitzer Fellowship Program, under award 1256317. This research has made use of the Sloan Digital Sky Survey ( Facilities: Spitzer, Sloan
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Spitzer Fellowship1256317
Subject Keywords:galaxies: active; quasars: general
Issue or Number:1
Record Number:CaltechAUTHORS:20100423-094938648
Persistent URL:
Official Citation:S. C. Gallagher et al 2007 ApJ 661 30 doi: 10.1086/513733
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18056
Deposited By: Jason Perez
Deposited On:23 Apr 2010 17:04
Last Modified:08 Nov 2021 23:41

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