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.