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 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 then 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 insights into the nature of the metallicity evolution mentioned above.

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