High-Redshift Galaxy Surveys and the Reionization of the Universe
  Star-forming galaxies in the early universe provide us with perhaps the most
natural way of explaining the reionization of the universe. Current
observational results are sufficiently comprehensive, as to allow us to
approximately calculate how the ionizing radiation from galaxies varies as a
function of cosmic time. Important uncertainties in modeling reionization by
galaxies revolve around the escape fraction and its luminosity and redshift
dependence, a possible truncation of the galaxy luminosity function at the
faint end, and an evolution in the production efficiency of Lyman-continuum
photons with cosmic time. Despite these uncertainties, plausible choices for
these parameters naturally predict a cosmic ionizing emissivity at z~6-10 whose
evolution and overall normalization is in excellent agreement with that derived
from current observational constraints. This strongly suggests that galaxies
provide the necessary photons to reionize the universe.
