IC 158 μm Probes of Damped Lyα Systems

摘要

Damped Lyn systems are a population of metal-enriched gaslayers that serve as important reservoirs of neutral gas for star formation athigh redshifts. This paper focuses on the interplay between stars and gas inthis population of protogalaxies. Specific attention is given to the multi-phasenature of the neutral gas inferred from measurements of the [C II] 158 pm coolingrate obtained from studies of CII~*λ1335.7 absorption. These results are used toestimate star formation rates: evidence is presented for a bimodal distributionof objects with and without ongoing star formation. We use the cooling rates to estimate flux densities of redshifted [CII]158 μm radiation, which can bemeasured with ALMA. Such measurements determine the dark-matter massesof halos in which the gas is located and discriminate among competing modelsof galaxy formation.