Hydrodynamical Simulations of Lyα Clouds

Abstract

Very recent work by Petitjean et al. (1995) and Mücket et al. (1995) have shown that the z-dependence of the number density of Lyα absorption lines and the large number of lines detected by HST at low z both can be understood if the Lyman α gas follows the filamentary structures of the dark matter. In an attempt to understand the physical state of the gas, we have modified a 1D-hydrodynamical code to include photoionization and cooling of the baryonic material. We present here preliminary results showing under which conditions the gas can survive down to very low redshifts.