Spectroscopic Identification of Type 2 Quasars at Z < 1 in SDSS-III/BOSS

Abstract

The physics and demographics of type 2 quasars remain poorly understood, and new samples of such objects selected in a variety of ways can give insight into their physical properties, evolution, and relationship to their host galaxies. We present a sample of 2758 type 2 quasars at z $\leq$ 1 from the SDSS-III/BOSS spectroscopic database, selected on the basis of their emission-line properties. We probe the luminous end of the population by requiring the rest-frame equivalent width of [OIII] to be > 100 {\AA}. We distinguish our objects from star-forming galaxies and type 1 quasars using line widths, standard emission line ratio diagnostic diagrams at z < 0.52 and detection of [Ne V]{\lambda}3426{\AA} at z > 0.52. The majority of our objects have [OIII] luminosities in the range 10^8.5-10^10 L$_{\odot}$ and redshifts between 0.4 and 0.65. Our sample includes over 400 type 2 quasars with incorrectly measured redshifts in the BOSS database; such objects often show kinematic substructure or outflows in the [OIII] line. The majority of the sample has counterparts in the WISE survey, with median infrared luminosity {\nu}L{\nu}[12{\mu}m] = 4.2 x 10^44 erg/sec. Only 34 per cent of the newly identified type 2 quasars would be selected by infrared color cuts designed to identify obscured active nuclei, highlighting the difficulty of identifying complete samples of type 2 quasars. We make public the multi-Gaussian decompositions of all [OIII] profiles for the new sample and for 568 type 2 quasars from SDSS I/II, together with non-parametric measures of line profile shapes and identify over 600 candidate double-peaked [OIII] profiles.