Growth of First Galaxies: Impacts of Star Formation and Stellar Feedback
  We present the results of cosmological hydrodynamic simulations with zoom-in
initial conditions, and investigate the formation of the first galaxies and
their evolution towards observable galaxies at $z \sim 6$. We focus on three
different galaxies which end up in halos with masses $M_{h} = 2.4
\times10^{10}~h^{-1}\; M_{\odot}$ (Halo-10), $1.6 \times10^{11}~h^{-1}\;
M_{\odot}$ (Halo-11) and $0.7 \times10^{12}~h^{-1} M_{\odot}$ (Halo-12) at z=6.
Our simulations also probe impacts of different sub-grid assumptions, i.e., SF
efficiency and cosmic reionization, on SF histories in the first galaxies. We
find that star formation occurs intermittently due to supernova (SN) feedback
at z > 10, and then it proceeds more smoothly as the halo mass grows at lower
redshifts. Galactic disks are destroyed due to SN feedback, while galaxies in
simulations with no-feedback or lower SF efficiency models can sustain galactic
disk for long periods > 10 Myr. The expulsion of gas at the galactic center
also affects the inner dark matter density profile. However, SN feedback does
not seem to keep the shallow profile of dark matter for a long period. Our
simulated galaxies in Halo-11 and Halo-12 reproduce the star formation rates
(SFR) and stellar masses of observed Lyman-$\alpha$ emitters (LAEs) at z = 7-8
fairly well given observational uncertainties. In addition, we investigate the
effect of UV background radiation on star formation as an external feedback
source, and find that earlier reionization extends the quenching time of star
formation due to photo-ionization heating, but does not affect the stellar mass
at z=6.
