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 63003 gravitating particles in a cubic box of Lbox = 3150 h−1Mpc, we build a dense forest of halo merger trees to trace the halo merger history with a halo mass resolution scale down to Ms = 2.7 × 1011h−1M⊙. 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/σ). 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 μ 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.

Abstract
1. INTRODUCTION
2. GOTPM CODE AND SIMULATION
    2.1. Initial Conditions and Parallelism
    2.2. Non-recursive Oct-Sibling Tree
    2.3. Position Accuracy in GOTPM
    2.4. Simulation Specifics
3. OUTPUT
    3.1. Snapshot and Past Lightcone Space Data
    3.2. Halo Merger Data
4. PROPERTIES OF FOF HALOS
    4.1. Multiplicity Function
    4.2. Halo Shape
    4.3. Halo Orientations
5. TWO-POINT CORRELATION FUNCTION
6. MASS ACCRETION HISTORY
7. SUMMARY
REFERENCES

• Juhan Kim(Center for Advanced Computation, Korea Institute for Advanced Study)
• Changbom Park(School of Physics, Korea Institute for Advanced Study)
• Benjamin L’Huillier(School of Physics, Korea Institute for Advanced Study) Corresponding author
• Sungwook E. Hong(School of Physics, Korea Institute for Advanced Study)