Fluctuating feedback-regulated escape fraction of ionizing radiation in
  low-mass, high-redshift galaxies
  Low mass galaxies are thought to provide the bulk of the ionizing radiation
necessary to reionize the Universe. The amount of photons escaping the galaxies
is poorly constrained theoretically, and difficult to measure observationally.
Yet it is an essential parameter of reionization models. We study in detail how
ionizing radiation can leak from high redshift galaxies. For this purpose, we
use a series of high resolution radiation hydrodynamics simulations, zooming on
three dwarf galaxies in a cosmological context. We find that the energy and
momentum input from the supernova explosions has a pivotal role in regulating
the escape fraction, by disrupting dense star forming clumps, and clearing
sight lines in the halo. In the absence of supernovae, photons are absorbed
very locally, within the birth clouds of massive stars. We follow the time
evolution of the escape fraction, and find that it can vary by more than six
orders of magnitude. This explains the large scatter in the value of the escape
fraction found by previous studies. This fast variability also impacts the
observability of the sources of reionization: a survey even as deep as $M_{\rm
UV} = -14$ would miss about half of the underlying population of
Lyman-continuum emitters.
