Star formation and clumps in cosmological galaxy simulations with radiation pressure feedback

Abstract

Cosmological simulations of galaxies have typically produced too many stars at early times. We study the global and morphological eects of radiation pressure (RP) in eight pairs of high-resolution cosmological galaxy formation simulations. We nd that the additional feedback suppresses star formation globally by a factor of 2. Despite this reduction, the simulations still overproduce stars by a factor of 2 with respect to the predictions provided by abundance matching methods for halos more massive than 5 10 11 M h 1 (Behroozi, Wechsler & Conroy 2013). We also study the morphological impact of radiation pressure on our simulations. In simulations with RP the average number of low mass clumps falls dramatically. Only clumps with stellar masses Mclump=Mdisk 6 5% are impacted by the inclusion of RP, and RP and no-RP clump counts above this range are comparable. The inclusion of RP depresses the contrast ratios of clumps by factors of a few for clump masses less than 5% of the disk masses. For more massive clumps, the dierences between and RP and no-RP simulations diminish. We note however, that the simulations analysed have disk stellar masses below about 2 10 10 M h 1 . By creating mock Hubble Space Telescope observations we