The impacts of ultraviolet radiation feedback on galaxies during the
  epoch of reionization
  We explore the impacts of ultraviolet (UV) radiation feedback on galaxies
during the epoch of reionisation by cosmological simulations in which
hydrodynamics and the transfer of the H and He ionising photons are
consistently coupled. Moreover we take into account H_2 non-equilibrium
chemistry, including photo-dissociation. The most striking feature of the
simulations is a high spatial resolution for the radiative transfer (RT)
calculation which enables us to start considering not only external UV feedback
processes but also internal UV feedback processes in each galaxy. We find that
the star formation is significantly suppressed due to the internal UV and
supernova (SN) feedback. In low mass galaxies with M<10^9Msun, a large amount
of gas is evacuated by photo-evaporation as previous studies have shown, which
results in the suppression of star formation. Surprisingly, star formation in
massive halos is also strongly suppressed despite the fact that these halos
hardly lose any gas by photo-evaporation. The suppression of star formation in
massive halos is mainly caused by following two factors; (i) small scale clumpy
structures in the galaxies are smoothened by the internal feedback, (ii)
although the dense gas in the galaxies is mostly neutral, the H_2 formation and
cooling processes are disturbed by mild photo-heating. Photo-dissociating
radiations actually suppress star formation, but the magnitude of the effect is
not so large in massive galaxies. Even though our simulation volume is too
small to be a representative patch of the Universe during reionisation, we find
that our simulated star formation rate densities and HI fractions at z=6-7 are
consistent with those found in observations.
