SPACE DENSITY OF OPTICALLY SELECTED TYPE 2 QUASARS

Abstract

Type 2 quasars are luminous active galactic nuclei (AGN) whose central\nregions are obscured by large amounts of gas and dust. In this paper, we\npresent a catalog of type 2 quasars from the Sloan Digital Sky Survey (SDSS),\nselected based on their optical emission lines. The catalog contains 887\nobjects with redshifts z < 0.83; this is six times larger than the previous\nversion and is by far the largest sample of type 2 quasars in the literature.\nWe derive the [OIII]5008 luminosity function for 10^8.3 Lsun < L[OIII] < 10^10\nLsun (corresponding to intrinsic luminosities up to M[2400A]-28 mag or\nbolometric luminosities up to 4x10^47 erg/sec). This luminosity function\nprovides strong lower limits to the actual space density of obscured quasars,\ndue to our selection criteria, the details of the spectroscopic target\nselection, as well as other effects. We derive the equivalent luminosity\nfunction for the complete sample of type 1 (unobscured) quasars; then, we\ndetermine the ratio of type 2/type 1 quasar number densities. Our best data\nconstrain this ratio to be at least 1.5:1 for 10^8.3 Lsun < L[OIII] < 10^9.5\nLsun at z < 0.3, and at least 1.2:1 for L[OIII]=10^10 Lsun at 0.3 < z < 0.83.\nType 2 quasars are at least as abundant as type 1 quasars in the relatively\nnearby Universe (z < 0.8) for the highest luminosities.\n