SPACE DENSITY OF OPTICALLY SELECTED TYPE 2 QUASARS
SPACE DENSITY OF OPTICALLY SELECTED TYPE 2 QUASARS
复制标题
DOI：
10.1088/0004-6256/136/6/2373
复制
发表时间：
2008-01
期刊：
影响因子：
--
通讯作者：
R. Reyes;N. Zakamska;M. Strauss;J. Green;J. Krolik;Yue Shen;G. Richards;S. Anderson;D. Schneide
中科院分区：
文献类型：
--
作者：
R. Reyes;N. Zakamska;M. Strauss;J. Green;J. Krolik;Yue Shen;G. Richards;S. Anderson;D. Schneide
2型类星体是明亮的活动星系核，其中心区域被大量气体和尘埃遮蔽。在本文中，我们提出了一份来自斯隆数字巡天的2型类星体的目录，这些类星体是根据它们的光学发射线选择的。该星表包含887个红移z < 0.83的天体；这比之前的版本大6倍，是迄今为止文献中最大的2型类星体样本。我们推导出108.3 L☉< L[O iii] < 1010 L☉的[O iii]5007亮度函数（LF）（对应于本质亮度高达M[2500 Å]高达4 × 1047 erg s−1的热光度）。由于我们的选择标准、光谱目标选择的细节和其他影响，这个LF为被遮蔽类星体的实际空间密度提供了强有力的下限。我们导出了1型（未遮挡）类星体完整样本的等效LF，并确定了2型与1型类星体数密度的比值。我们的数据约束这个比值至少为~ 1.5:1，对于108.3 L☉< L[O iii] < 109.5 L☉，在z < 0.3，对于L[O iii] ~ 1010 L☉，在0.3 < z < 0.83，至少为~ 1.2:1。在相对较近的宇宙中（z > 0.8）， 2型类星体的数量至少和1型类星体一样多。
Type 2 quasars are luminous active galactic nuclei whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey, selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is 6 times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [O iii]5007 luminosity function (LF) for 108.3 L☉ < L[O iii] < 1010 L☉ (corresponding to intrinsic luminosities up to M[2500 Å] ≃ −28 mag or bolometric luminosities up to 4 × 1047 erg s−1). This LF provides robust lower limits to the actual space density of obscured quasars due to our selection criteria, the details of the spectroscopic target selection, and other effects. We derive the equivalent LF for the complete sample of type 1 (unobscured) quasars and determine the ratio of type 2 to type 1 quasar number densities. Our data constrain this ratio to be at least ∼1.5:1 for 108.3 L☉ < L[O iii] < 109.5 L☉ at z < 0.3, and at least ∼1.2:1 for L[O iii] ∼ 1010 L☉ at 0.3 < z < 0.83. Type 2 quasars are at least as abundant as type 1 quasars in the relatively nearby universe (z ≲ 0.8) for the highest luminosities.