Fragmentation In The First Galaxies

Abstract

Using a one-zone model, we study the gravitational fragmentation of baryonic cold streams flowing into a typical first galaxy at high redshift to predict the expected fragmentation mass scale and thus a characteristic mass of the first population of stars to form by shock fragmentation. In this simplified model, we bypass the resolution barrier in simulations of progalaxy formation and directly probe the fragmentation mass scale of accreting gas streams. We find the fragmentation mass scale to be most strongly dependent on the metallicity of the gas and the background Lyman-Werner radiation field, and that either a large cluster of solar mass fragments or one large (10(5) M(circle dot)) fragment forms.