THE LARGE BRIGHT QSO SURVEY FOR DAMPED Lyα ABSORPTION SYSTEMS

摘要

We present a new survey for damped Lyα systems with redshifts z ≈ 1.6-3.0. The survey is based on a sample of 228 QSOs drawn from the Large Bright QSO Survey (LBQS). We find a total of 20 candidate damped Lyα lines with rest frame equivalent widths determined from low-resolution spectroscopy of W ≥ 10 A. Using intermediate-resolution spectroscopy, we and other workers confirm 12 of these candidates and an additional candidate with W < 10 A as damped Lyα systems with H I column densities N(H I) ≥ 2 x 10~(20) cm~(-2). All the systems were drawn from a redshift path Δz = 121.0 along which it is possible to detect damped Lyα candidates with W ≥ 5 A at 5 σ statistical significance. We combine the results of the LBQS damped survey with results of previous surveys for damped systems to form a " statistical sample" of 62 damped Lyα systems with N(H I) ≥ 2 x 10~(20) cm~(-2). These systems are drawn from a total redshift path Δz = 323.8. A list of 18 additional damped Lyα systems not found in systematic surveys is also presented. Therefore, we are aware of 80 damped Lyα absorption systems at the time of writing (1995 March) with N(H I) ≥ 2 x 10~(20) cm~(-2). The following is a summary of results based on the " statistical sample."