Spatially adaptive radiation-hydrodynamical simulations of galaxy
  formation during cosmological reionization
  We present a suite of cosmological radiation-hydrodynamical simulations of
the assembly of galaxies driving the reionization of the intergalactic medium
(IGM) at z >~ 6. The simulations account for the hydrodynamical feedback from
photoionization heating and the explosion of massive stars as supernovae (SNe).
Our reference simulation, which was carried out in a box of size 25 comoving
Mpc/h using 2 x 512^3 particles, produces a reasonable reionization history and
matches the observed UV luminosity function of galaxies. Simulations with
different box sizes and resolutions are used to investigate numerical
convergence, and simulations in which either SNe or photoionization heating or
both are turned off, are used to investigate the role of feedback from star
formation. Ionizing radiation is treated using accurate radiative transfer at
the high spatially adaptive resolution at which the hydrodynamics is carried
out. SN feedback strongly reduces the star formation rates (SFRs) over nearly
the full mass range of simulated galaxies and is required to yield SFRs in
agreement with observations. Photoheating helps to suppress star formation in
low-mass galaxies, but its impact on the cosmic SFR is small. Because the
effect of photoheating is masked by the strong SN feedback, it does not imprint
a signature on the UV galaxy luminosity function, although we note that our
resolution is insufficient to model star-forming minihaloes cooling through
molecular hydrogen transitions. Photoheating does provide a strong positive
feedback on reionization because it smooths density fluctuations in the IGM,
which lowers the IGM recombination rate substantially. Our simulations
demonstrate a tight non-linear coupling of galaxy formation and reionization,
motivating the need for the accurate and simultaneous inclusion of photoheating
and SN feedback in models of the early Universe.
