April 20
Arthur M. Wolfe (University of California, San
Diego)
Damped Lyman Alpha Absorption Systems: Neutral
Gas Reservoirs for Star Formation in Early Galaxies
Damped
Lyman-alpha absorption systems (DLAs) are gas layers that dominate the
neutral-gas content of the Universe in the redshift interval z=[0,5] and serve
as neutral-gas reservoirs for star formation in early galaxies. I first discuss results of our recent
Keck survey for the DLAs out to z=5. I focus on evolution of the metal content
of the gas, emphasizing the connection between DLAs and stars in the Milky-Way
halo. I next discuss the star formation
efficiency of neutral gas in DLAs. I
focus on two independent tests indicating that the efficiency of star formation
in DLAs is far below that indicated by the standard Kennicutt-Schmidt relation. Finally, I discuss DLA kinematics. I show how the frequency distribution of
velocity intervals obtained from low-ion absorption lines presents a challenge
for hierarchical models, but at the same time provides new insight into the
natureof the metallicity evolution mentioned above.