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Space density of optically-selected type 2 quasars
Journal article   Open access

Space density of optically-selected type 2 quasars

Reinabelle Reyes, Nadia L Zakamska, Michael A Strauss, Joshua Green, Julian H Krolik, Yue Shen, Gordon Richards, Scott Anderson and Donald Schneider
The Astronomical journal, v 136(6), pp 2373-2390
08 Jan 2008
DOI: https://doi.org/10.1088/0004-6256/136/6/2373
url
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.245.4668View
SubmittedOpen Access (License Unspecified),  Open
url
https://doi.org/10.1088/0004-6256/136/6/2373View
Published, Version of Record (VoR) Open

Abstract

Physics - Astrophysics of Galaxies Physics - Cosmology and Nongalactic Astrophysics Physics - Earth and Planetary Astrophysics Physics - High Energy Astrophysical Phenomena Physics - Instrumentation and Methods for Astrophysics Physics - Solar and Stellar Astrophysics
Astron.J.136:2373-2390,2008;Astron.J.139:1295-1296,2010 Type 2 quasars are luminous active galactic nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey (SDSS), selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is six times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [OIII]5008 luminosity function for 10^8.3 Lsun < L[OIII] < 10^10 Lsun (corresponding to intrinsic luminosities up to M[2400A]-28 mag or bolometric luminosities up to 4x10^47 erg/sec). This luminosity function provides strong lower limits to the actual space density of obscured quasars, due to our selection criteria, the details of the spectroscopic target selection, as well as other effects. We derive the equivalent luminosity function for the complete sample of type 1 (unobscured) quasars; then, we determine the ratio of type 2/type 1 quasar number densities. Our best data constrain this ratio to be at least 1.5:1 for 10^8.3 Lsun < L[OIII] < 10^9.5 Lsun at z < 0.3, and at least 1.2:1 for L[OIII]=10^10 Lsun at 0.3 < z < 0.83. Type 2 quasars are at least as abundant as type 1 quasars in the relatively nearby Universe (z < 0.8) for the highest luminosities.

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