The formation of disk galaxies at high redshift - Observations of damped Lyman-alpha absorption in high redshift QSOs

Abstract

We present here observations at 3 Å resolution which confirm damped Lyα profiles for a number of candidate galaxy disk absorption systems in a sample of high-redshift QSOs. A combination of strong, self-damped Lyα absorption plus blended narrow absorption features adequately fits the data for 18 systems in 15 objects. This is at least a factor of five in excess of the number of galaxy disks expected to be intercepted by lines of sight to this sample of QSOs. These results imply that approximately 20% of the sky is covered by gaseous disks to a column density, N<SUB>H I</SUB> &gt; 2 × 10<SUP>20</SUP> cm<SUP>-2</SUP> in the redshift interval z 2-3. We suggest that gaseous disks form relatively early in galaxies and that they may be considerably larger at early epochs.