Damped Lyman Alpha Systems in Galaxy Formation Simulations

Abstract

We investigate the population of z = 3 damped Lyman alpha systems (DLAs) in a recent series of high resolution galaxy formation simulations. The simulations are of interest because they form at z = 0 some of the most realistic disk galaxies to date. No free parameters are available in our study: the simulation parameters have been fixed by physical and z = 0 observational constraints, and thus our work provides a genuine consistency test. The precise role of DLAs in galaxy formation remains in debate, but they provide a number of strong constraints on the nature of our simulated bound systems at z = 3 because of their coupled information on neutral H I densities, kinematics, metallicity and estimates of star formation activity. Our results, without any parameter-tuning, closely match the observed incidence rate and column density distributions of DLAs. Our simulations are the first to reproduce the distribution of metallicities (with a median of ZDLA ≃ Z⊙/20) without invoking observationally unsupported mechanisms such as significant dust biasing. This is especially encouraging given that these simulations have previously been shown to have a realistic 0 < z < 2 stella

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