Dark-ages reionization and galaxy formation simulation - III. Modelling
  galaxy formation and the epoch of reionization
  We introduce Meraxes, a new, purpose-built semi-analytic galaxy formation
model designed for studying galaxy growth during reionization. Meraxes is the
first model of its type to include a temporally and spatially coupled treatment
of reionization and is built upon a custom (100 Mpc)$^3$ N-body simulation with
high temporal and mass resolution, allowing us to resolve the galaxy and star
formation physics relevant to early galaxy formation. Our fiducial model with
supernova feedback reproduces the observed optical depth to electron scattering
and evolution of the galaxy stellar mass function between $z$=5 and 7,
predicting that a broad range of halo masses contribute to reionization. Using
a constant escape fraction and global recombination rate, our model is unable
to simultaneously match the observed ionizing emissivity at $z{\lesssim}6$.
However, the use of an evolving escape fraction of 0.05-0.1 at $z{\sim}6$,
increasing towards higher redshift, is able to satisfy these three constraints.
We also demonstrate that photoionization suppression of low mass galaxy
formation during reionization has only a small effect on the ionization history
of the inter-galactic medium. This lack of `self-regulation' arises due to the
already efficient quenching of star formation by supernova feedback. It is only
in models with gas supply-limited star formation that reionization feedback is
effective at regulating galaxy growth. We similarly find that reionization has
only a small effect on the stellar mass function, with no observationally
detectable imprint at $M_{\rm *}{>}10^{7.5}\,{\rm M_{{\odot}}}$. However,
patchy reionization has significant effects on individual galaxy masses, with
variations of factors of 2-3 at $z$=5 that correlate with environment.
