The Cosmological Evolution of Quasar Damped Lyman-Alpha Systems
Sandhya Rao
Abstract
We present results from an efficient, non-traditional survey to discover damped Lyman-alpha (DLA) absorption-line systems with neutral hydrogen column densities N(HI)>2x1020 atoms cm-2 and redshifts z<1.65. Contrary to previous studies at higher redshift that showed a decrease in the cosmological mass density of neutral gas in DLA absorbers, OmegaDLA, with time, our results indicate that OmegaDLA is consistent with remaining constant from redshifts z ≈ 4 to z ≈ 0.5. There is no evidence that OmegaDLA is approaching the value at z=0. Other interesting results from the survey are also presented.
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