Candidate type II quasars from the sloan digital sky survey. I. Selection and optical properties of a sample at 0.3 < Z < 0.83

Nadia L. Zakamska, Michael A. Strauss, Julian H. Krolik, Matthew J. Collinge, Patrick B. Hall, Lei Hao, Timothy M. Heckman, Željko Ivezić, Gordon T. Richards, David J. Schlegel, Donald P. Schneider, Iskra Strateva, Daniel E. Vanden Berk, Scott F. Anderson, Jon Brinkmann

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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 × 10 8-10 10 L , comparable to those of luminous (-27 < M B < -23) quasars; this, along with other evidence, suggests that the objects in the luminous subsample are type II quasars.

Original languageEnglish (US)
Pages (from-to)2125-2144
Number of pages20
JournalAstronomical Journal
Volume126
Issue number5 1775
DOIs
StatePublished - Nov 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Galaxies: active
  • Quasars: emission lines
  • Quasars: general
  • Surveys

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    Zakamska, N. L., Strauss, M. A., Krolik, J. H., Collinge, M. J., Hall, P. B., Hao, L., Heckman, T. M., Ivezić, Ž., Richards, G. T., Schlegel, D. J., Schneider, D. P., Strateva, I., Vanden Berk, D. E., Anderson, S. F., & Brinkmann, J. (2003). Candidate type II quasars from the sloan digital sky survey. I. Selection and optical properties of a sample at 0.3 < Z < 0.83. Astronomical Journal, 126(5 1775), 2125-2144. https://doi.org/10.1086/378610