We employ high-resolution cosmological zoom-in simulations focusing on a
high-sigma peak and an average cosmological field at z∼6−12, in order to
investigate the influence of environment and baryonic feedback on galaxy
evolution in the reionization epoch. Strong feedback, e.g., galactic winds,
caused by elevated star formation rates (SFRs) is expected to play an important
role in this evolution. We compare different outflow prescriptions: (i)
constant wind velocity (CW), (ii) variable wind scaling with galaxy properties
(VW), and (iii) no outflows (NW). The overdensity leads to accelerated
evolution of dark matter and baryonic structures, absent in the "normal"
region, and to shallow galaxy stellar mass functions at the low-mass end.
Although CW shows little dependence on both environments, the more physically
motivated VW model does exhibit this effect. In addition, VW can reproduce the
observed specific SFR (sSFR) and the sSFR-stellar mass relation, which CW and
NW fail to satisfy simultaneously. Winds also differ substantially in affecting
the state of the intergalactic medium (IGM). The difference lies in
volume-filling factor of hot, high-metallicity gas which is near unity for CW,
while it remains confined in massive filaments for VW, and locked up in
galaxies for NW. Such gas is nearly absent in the normal region. Although all
wind models suffer from deficiencies, the VW model seems to be promising in
correlating the outflow properties to those of host galaxies. Further
constraints on the state of the IGM at high-z are needed to separate
different wind models.Comment: 22 pages, 15 figures, accepted for publication in the Astrophysical
Journa
