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An Investigation into the Effects of Luminosity on the Mid-Infrared Spectral Energy Distributions of Radio-Quiet Quasars
Journal article   Open access

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

S. C Gallagher, G. T Richards, M Lacy, D. C Hines, M Elitzur and L. J Storrie-Lombardi
The Astrophysical journal, v 661(1 I), pp 30-37
09 Feb 2007
url
https://doi.org/10.1086/513733View
Published, Version of Record (VoR) Open

Abstract

Physics - Cosmology and Nongalactic Astrophysics Physics - Earth and Planetary Astrophysics Physics - Instrumentation and Methods for Astrophysics Physics - High Energy Astrophysical Phenomena Physics - Solar and Stellar Astrophysics Physics - Astrophysics of Galaxies
Astrophys.J.661:30-37,2007 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 micron 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 this trend is likely a manifestation of the `near-infrared (3-5 micron) bump' noticed 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 micron luminosity as well as its lack of sensitivity to dust extinction as compared to the standard bolometric correction from nu*L_{5100A} 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.

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Astronomy & Astrophysics
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