Reproducing the kinematics of damped Lyman α systems

We examine the kinematic structure of Damped Lyman- Systems (DLAs) in a series of cosmological hydrodynamic simulations using the AREPO code. We are able to match the distribution of velocity widths of associated low ionisation metal absorbers substantially better than earlier work. Our simulations produce a population of DLAs dominated by halos with virial velocities around 70 km s 1 , consistent with a picture of relatively small, faint objects. In addition, we reproduce the observed correlation between velocity width and metallicity and the equivalent width distribution of SiII. Some discrepancies of moderate statistical signicance remain; too many of our spectra show absorption concentrated at the edge of the prole and there are slight dierences in the exact shape of the velocity width distribution. We show that the improvement over previous work is mostly due to our strong feedback from star formation and our detailed modelling of the metal ionisation state.