Horizon Run 4 Simulation: Coupled Evolution of Galaxies and Large-scale
  Structures of the Universe
  The Horizon Run 4 is a cosmological $N$-body simulation designed for the
study of coupled evolution between galaxies and large-scale structures of the
Universe, and for the test of galaxy formation models. Using $6300^3$
gravitating particles in a cubic box of $L_{\rm box} = 3150 ~h^{-1}{\rm Mpc}$,
we build a dense forest of halo merger trees to trace the halo merger history
with a halo mass resolution scale down to $M_s = 2.7 \times 10^{11} h^{-1}{\rm
M_\odot}$. We build a set of particle and halo data, which can serve as
testbeds for comparison of cosmological models and gravitational theories with
observations. We find that the FoF halo mass function shows a substantial
deviation from the universal form with tangible redshift evolution of amplitude
and shape. At higher redshifts, the amplitude of the mass function is lower,
and the functional form is shifted toward larger values of $\ln (1/\sigma)$. We
also find that the baryonic acoustic oscillation feature in the two-point
correlation function of mock galaxies becomes broader with a peak position
moving to smaller scales and the peak amplitude decreasing for increasing
directional cosine $\mu$ compared to the linear predictions. From the halo
merger trees built from halo data at 75 redshifts, we measure the half-mass
epoch of halos and find that less massive halos tend to reach half of their
current mass at higher redshifts. Simulation outputs including snapshot data,
past lightcone space data, and halo merger data are available at
http://sdss.kias.re.kr/astro/Horizon-Run4/.
