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Redshift Distribution and Luminosity Functions of Obscured and Unobscured Quasars

Published online by Cambridge University Press:  25 July 2014

Susan E. Ridgway ,
M. Lacy ,
A. Petric ,
A. Sajina ,
T. Urrutia  and
E. L. Gates
Susan E. Ridgway
Affiliation:
National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA email: ser@noao.edu
M. Lacy
Affiliation:
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903, USA
A. Petric
Affiliation:
California Institute of Technology, Pasadena, CA 91125
A. Sajina
Affiliation:
Department of Physics and Astronomy, Tufts University, 212 College Avenue, Medford, MA 02155, USA
T. Urrutia
Affiliation:
Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482, Potsdam, Germany
E. L. Gates
Affiliation:
UCO/Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140
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Abstract

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We have undertaken a spectroscopic survey of luminous AGNs and quasars selected in the mid-infrared from Spitzer IRAC surveys. Mid-infrared selection is much less biased with respect to obscuration than optical techniques, and hence enables the discovery of obscured quasars as well as normal, unobscured ones. Our survey is designed to include brighter 24 micron sources over wider areas and also to go to much lower fluxes limits in more limited spatial regions to allow us to disentangle dependences on redshift and luminosity. We have used 4m class telescopes to obtain spectra of the brighter 24 micron targets (targeting high luminosity objects at low z), and 8m class telescopes to identify lower luminosity high-redshift obscured quasars by targeting the fainter 24 micron targets. Fron this survey we have been able to compile a statistically complete sample of ~ 500 AGN, both obscured and unobscured, over a large range of redshift and luminosity. We find that obscured objects outnumber unobscured AGN with an obscured fraction ranging from ~ 90% to ~ 50%. For the most luminous quasars, the number densities of unobscured quasars peaks at z ~ 2.8, and for the obscured objects, the peak may be at slightly higher redshift.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S304: Multiwavelength AGN Surveys and Studies , October 2013 , pp. 61 - 64
Copyright
Copyright © International Astronomical Union 2014 

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