Effect of Cosmic UV Background on Star Formation in High Redshift Galaxies

Abstract

The effect of the cosmic UV background on star formation in high redshift galaxies is explored by means of high resolutions cosmological simulations. The simulations include star formation, 3D radiative transfer, and a highly detailed ISM model, and reach spatial resolution sufficient to resolve formation sites for molecular clouds. In the simulations the local radiation field in the Lyman-Werner band around star-forming molecular clouds dominates over the cosmic UV background by a factor of 100, similarly to the interstellar radiation field in the Milky Way and in a few high redshift galaxies for which measurements exist. The cosmic UV background, therefore, is essentially irrelevant for star formation in normal galaxies.