IONIZING RADIATION FROM z=4-10 GALAXIES

We compute the escape of ionizing radiation from galaxies in the redshift interval z = 4-10, i.e., during and after the epoch of reionization, using a high-resolution set of galaxies, formed in fully cosmological simulations. The simulations invoke early, energetic feedback, and the galaxies evolve into a realistic population at z = 0. Our galaxies cover nearly four orders of magnitude in masses (10(7.8)-10(11.5)M(circle dot)) and more than five orders in star formation rates (10(-3.5)-10(1.7)M(circle dot) yr(-1)), and we include an approximate treatment of dust absorption. We show that the source-averaged Lyman limit escape fraction at z = 10.4 is close to 80% declining monotonically with time as more massive objects build up at lower redshifts. Although the amount of dust absorption is uncertain to 1-1.5 dex, it is tightly correlated with metallicity; we find that dust is unlikely to significantly impact the observed UV output. These results support reionization by stellar radiation from low-luminosity dwarf galaxies and are also compatible with Lyman continuum observations and theoretical predictions at z similar to 3-4.