Broad Absorption Line Quasars in the SDSS

The Sloan Digital Sky Survey Early Data Release yielded a sample of 224 broad absorption line quasars, the largest sample compiled to date. Of these BALQSOs, 131 form a relatively complete and homogeneous sample. The quasars are classified as BALQSOs or nonBALQSOs based on the traditional balnicity index applied to broad C IV absorption. The balnicity index distribution suggests that the fraction of quasars with intrinsic outflows may be significantly underestimated by this traditional index. We find that nonBALQSOs, high-ionization BALQSOs (HiBALs), and low-ionization BALQSOs (LoBALs) form a sequence of quasars with increasing amounts of reddening. Upon correcting for color-dependent selection effects due to different SEDs of BALQSOs and nonBALQSOs, we find that the fraction of BALQSOs is 13.4 ± 1.2% and shows no significant redshift dependence for 1.7 ≤ z ≤ 3.45. After including a rough completeness correction for the effects of dust extinction within the uncertainties, we find that one in every six quasars is a BALQSO.