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Spectroscopic identification of type 2 quasars at z < 1 in SDSS-III/BOSS

Author(s): Yuan, Sihan; Strauss, Michael A; Zakamska, Nadia L

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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 1 from the Sloan Digital Sky Survey-III (SDSS-III)/Baryon Oscillation Spectroscopic Survey (BOSS) spectroscopic data base, 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 [O III] to be >100 Å. 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]λ3426 Å at z > 0.52. The majority of our objects have [O III] luminosities in the range 1.2 × 1042–3.8 × 1043 erg s−1 and redshifts between 0.4 and 0.65. Our sample includes over 400 type 2 quasars with incorrectly measured redshifts in the BOSS data base; such objects often show kinematic substructure or outflows in the [O III] line. The majority of the sample has counterparts in the Wide-field Infrared Survey Explorer survey, with median infrared luminosity νLν [12 μm] = 4.2 × 1044 erg s−1. Only 34 per cent of the newly identified type 2 quasars would be selected by infrared colour 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 [O III] profiles for the new sample and for 568 type 2 quasars from SDSS I/II, together with non-parametric measures of the [O III] line profile shapes. We also identify over 600 candidate double-peaked [O III] profiles.
Publication Date: 19-Jul-2016
Electronic Publication Date: 21-Oct-2016
Citation: Yuan, Sihan, Strauss, Michael A, Zakamska, Nadia L. (2016). Spectroscopic identification of type 2 quasars at z < 1 in SDSS-III/BOSS. \mnras, 462 (1603 - 1615. doi:10.1093/mnras/stw1747
DOI: doi:10.1093/mnras/stw1747
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Pages: 1603 - 1615
Type of Material: Journal Article
Journal/Proceeding Title: Monthly Notices of the Royal Astronomical Society
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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