Astraeus I: The interplay between galaxy formation and reionization
  We introduce a new self-consistent model of galaxy evolution and
reionization, ASTRAEUS (semi-numerical rAdiative tranSfer coupling of galaxy
formaTion and Reionization in N-body dArk mattEr simUlationS), which couples a
state-of-the-art N-body simulation with the semi-analytical galaxy evolution
DELPHI and the semi-numerical reionization scheme CIFOG. ASTRAEUS includes all
the key processes of galaxy formation and evolution (including accretion,
mergers, supernova and radiative feedback) and follows the time and spatial
evolution of the ionized regions in the intergalactic medium (IGM).
Importantly, it explores different radiative feedback models that cover the
physically plausible parameter space, ranging from a weak and delayed to a
strong and immediate reduction of gas mass available for star formation. From
our simulation suite that covers the different radiative feedback prescriptions
and ionization topologies, we find that radiative feedback continuously reduces
star formation in galaxies with $M_h<10^{9.5}M_{\odot}$ upon local
reionization; larger mass halos are unaffected even for the strongest and
immediate radiative feedback cases during reionization. For this reason, the
ionization topologies of different radiative feedback scenarios differ only on
scales smaller than $1-2$Mpc, and significant deviations are only found when
physical parameters (e.g. the escape fraction of ionizing photons) are altered
based on galactic properties. Finally, we find observables (the ultra-violet
luminosity function, stellar mass function, reionization histories and
ionization topologies) are hardly affected by the choice of the used stellar
population synthesis models that either model single stars or binaries.
