  We present the first gas dynamical simulations of the photoevaporation of
cosmological minihalos overtaken by the ionization fronts which swept through
the IGM during reionization in a LCDM universe, including the effects of
radiative transfer. We demonstrate the phenomenon of I-front trapping inside
minihalos, in which the weak, R-type fronts which traveled supersonically
across the IGM decelerated when they encountered the dense, neutral gas inside
minihalos, becoming D-type I-fronts, preceded by shock waves. For a minihalo
with virial temperature T_vir < 10,000 K, the I-front gradually burned its way
through the minihalo which trapped it, removing all of its baryonic gas by
causing a supersonic, evaporative wind to blow backwards into the IGM, away
from the exposed layers of minihalo gas just behind the advancing I-front.
  Such hitherto neglected feedback effects were widespread during reionization.
N-body simulations and analytical estimates of halo formation suggest that
sub-kpc minihalos such as these, with T_vir < 10,000 K, were so common as to
dominate the absorption of ionizing photons. This means that previous estimates
of the number of ionizing photons per H atom required to complete reionization
which neglected this effect may be too low. Regardless of their effect on the
progress of reionization, however, the minihalos were so abundant that random
lines of sight thru the high-z universe should encounter many of them, which
suggests that it may be possible to observe the processes described here in the
absorption spectra of distant sources.
