The Nature of Damped Lyman Alpha Systems and Their Hosts in the Standard Cold Dark Matter Universe

Using adaptive mesh-refinement cosmological hydrodynamic simulations with a physically motivated supernova feedback prescription we show that the stan-dard cold dark matter model can account for extant observed properties of damped Lyman alpha systems (DLAs). We then examine the properties of DLA host galaxies. We find: (1) While DLA hosts roughly trace the overall population of galaxies at all redshifts, they are always gas rich and have tendencies of be-ing slightly smaller and bluer. (2) The history of DLA evolution is cosmological in nature and reflects primarily the evolution of the underlying cosmic density, galaxy size and galaxy interactions. With higher density and more interactions at high redshift DLAs are larger in both absolute terms and in relative terms with respect to virial radii of halos. (3) The variety of DLAs at high redshift is richer with a large contribution coming from galactic filaments, created through close galaxy interactions. The portion of gaseous disks of galaxies where most stars reside makes relatively small contribution to DLA incidence at z = 3 − 4