A Damped Lyα Survey at z < 1.65

Abstract

We have used a new approach to study the evolutionary properties of damped Lyα systems at z < 1.65. The approach takes advantage of the fact that all damped Lyα systems studied so far are found to have corresponding MgII absorption. From known MgII absorption-line statistics, we determine an upper limit to the number of damped Lyα systems per unit redshift, n dl ya, at <z> ≈ 0.8 that is consistent with the trend at higher redshift as well as the number density at the current epoch. The data exhibit a trend established by three different observing techniques over three redshift regimes, providing important evidence that this trend actually traces the evolution of neutral gas in galaxies. Implications for the evolution of n dl ya(z) and the cosmological neutral hydrogen gas mass density,Ω hi(z), are discussed.KeywordsStar FormationHigh RedshiftStar Formation RatePresent EpochNearby GalaxyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.