Candidate Type II Quasars from the Sloan Digital Sky Survey. I. Selection and Optical Properties of a Sample at 0.3<Z<0.83
Abstract
Type II quasars are the long-sought luminous analogs of type 2 (narrow emission line) Seyfert galaxies, suggested by unification models of active galactic nuclei (AGNs) and postulated to account for an appreciable fraction of the cosmic hard X-ray background. We present a sample of 291 type II AGNs at redshifts 0.3<Z<0.83 from the spectroscopic data of the Sloan Digital Sky Survey. These objects have narrow (FWHM<2000 km s-1), high equivalent width emission lines with high-ionization line ratios. We describe the selection procedure and discuss the optical properties of the sample. About 50% of the objects have [O III] λ5008 line luminosities in the range 3×108-1010Lsolar, comparable to those of luminous (-27<MB<-23) quasars; this, along with other evidence, suggests that the objects in the luminous subsample are type II quasars.
- Publication:
-
The Astronomical Journal
- Pub Date:
- November 2003
- DOI:
- arXiv:
- arXiv:astro-ph/0309551
- Bibcode:
- 2003AJ....126.2125Z
- Keywords:
-
- Galaxies: Active;
- Galaxies: Quasars: Emission Lines;
- Galaxies: Quasars: General;
- Surveys;
- Astrophysics
- E-Print:
- Accepted to AJ (November issue), 46 pages including 2 tables and 15 figures, the full version of Table 1 is available at http://www.astro.princeton.edu/~nadia/qso2.html
