Broad Absorption Line Quasars in the Sloan Digital Sky Survey with VLA FIRST Radio Detections

Abstract

We present 13 broad absorption line (BAL) quasars, including 12 new objects, identi—ed in the Sloan Digital Sky Survey (SDSS) and matched within 2A to sources in the FIRST radio survey catalog. The surface density of this sample of radio-detected BAL quasars is 4.5 ^ 1.2 per 100 deg2, i.e., approximately 4 times as high as previously found by the shallower FIRST Bright Quasar Survey (FBQS). A majority of these radio-detected BAL quasars are moderately radio-loud objects. The fraction of BAL quasars in the entire radio quasar sample, 4.8% ^ 1.3%, is comparable to the fraction of BAL quasars among the SDSS optical quasar sample (ignoring selection eUects). We estimate that the true fraction of BAL quasars (mostly ii HiBALs ˇˇ) in the radio sample is 9.2% ^ 2.6%, once selection eUects are accounted for. We caution that the absorption troughs of four of the 13 radio-detected quasars considered do not strictly satisfy the standard BALnicity criteria. One or possibly two of the new radio-detected BAL quasars are of the rare ii FeLoBAL ˇˇ type. BAL quasars are generally redder than the median SDSS quasar at the same redshift. ”