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High Signal-to-Noise Ratio Mid-Infrared Quasar Spectral Templates

Published online by Cambridge University Press:  25 July 2014

Allison R. Hill ,
S. C. Gallagher ,
R. P. Deo ,
E. Peeters  and
Gordon T. Richards
Allison R. Hill
Affiliation:
The University of Western Ontario, 1151 Richmond Street, London, ON, N6A3K7, Canada email: [email protected]
S. C. Gallagher
Affiliation:
The University of Western Ontario, 1151 Richmond Street, London, ON, N6A3K7, Canada email: [email protected]
R. P. Deo
Affiliation:
The University of Western Ontario, 1151 Richmond Street, London, ON, N6A3K7, Canada email: [email protected]
E. Peeters
Affiliation:
The University of Western Ontario, 1151 Richmond Street, London, ON, N6A3K7, Canada email: [email protected] SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043, USA
Gordon T. Richards
Affiliation:
Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA Max Planck Institut für Astronomie, Königstuhl 17, Heidelberg, Germany69117
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Abstract

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Mid-infrared (MIR) quasar spectra exhibit a suite of emission features including high ionization coronal lines from the narrow line region (NLR) illuminated by the ionizing continuum, and hot dust features from grains, as well as polycyclic aromatic hydrocarbons (PAH) features from star formation in the host galaxy. Few features are detected in most spectra because of typically low signal-to-noise ratio (S/N) data. By generating spectral composites in three different luminosity bins from over 180 Spitzer Ifnfrared Spectrograph (IRS) observations, we boost the S/N and reveal important features in the complex spectra. We detect high-ionization, forbidden emission lines in all templates, PAH features in all but the most luminous objects, and broad silicate and graphite features in emission whose strength increases relative to the continuum with luminosity. We find that the intrinsic quasar spectrum for all luminosity templates is consistent, and the differences in the spectra can be explained by host galaxy contamination in the lower luminosity templates. We also posit that star formation may be active in most quasar host galaxies, but the spectral features of star formation are only detectable if the quasar is faint.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S304: Multiwavelength AGN Surveys and Studies , October 2013 , pp. 315 - 318
Copyright
Copyright © International Astronomical Union 2014 

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