## Scientific Purpose

We present two large cosmological N-body simulations, called Horizon Run 2 (HR2) and Horizon Run 3 (HR3), made using $6000^3$ = 216 billions and $7210^3$ = 374 billion particles, spanning a volume of $(7.200 h^{-1} \mathrm{Gpc})^3$ and $(10.815 h^{-1} \mathrm{Gpc})^3$, respectively. These simulations improve on our previous Horizon Run 1 (HR1) up to a factor of 4.4 in volume, and range from 2600 to over 8800 times the volume of the Millennium Run. In addition, they achieve a considerably finer mass resolution, down to $1.25\times 10^{11} h^{-1} M_\odot$, allowing to resolve galaxy-size halos with mean particle separations of $1.2h^{-1} \mathrm{Mpc}$ and $1.5h^{-1} \mathrm{Mpc}$, respectively. We have measured the power spectrum, correlation function, mass function and basic halo properties with percent level accuracy, and verified that they correctly reproduce the $\Lambda$CDM theoretical expectations, in excellent agreement with linear perturbation theory. Our unprecedentedly large-volume N-body simulations can be used for a variety of studies in cosmology and astrophysics, ranging from large-scale structure topology, baryon acoustic oscillations, dark energy and the characterization of the expansion history of the Universe, till galaxy formation science - in connection with the new SDSS-III. To this end, we made a total of 35 all-sky mock surveys along the past light cone out to z=0.7 (8 from the HR2 and 27 from the HR3), to simulate the BOSS geometry. The simulations and mock surveys are already publicly available on this page (to download the preprint, click here.)

## Authors

- Juhan Kim at CAC of Korea Institute for Advanced Study (KIAS; email contact: kjhan _at_ kias.re.kr)
- Changbom Park at KIAS
- Graziano Rossi at KIAS (corresponding author: graziano _at_ kias.re.kr)
- Sang Min Lee at Korea Institute of Science and Technology Information
- J.Richard Gott III at Princeton University

## Cosmological model of the Horizon Runs (HR's)

All the HR's share the same cosmology.

### Cosmological parameters of the HR's

Cosmological model | $\Omega_{m,0}$ | $\Omega_{b,0}$ | $\Omega_{\Lambda,0}$ | $n_\mathrm{s}$ | $H_0$ (km/s/Mpc) | $\sigma_8$ |
---|---|---|---|---|---|---|

$\Lambda$CDM WMAP5 | 0.26 | 0.044 | 0.74 | 0.96 | 72 | 1/1.26 |

### Simulations specifics

Simulations Name | HR1 | HR2 | HR3 | HR4 |
---|---|---|---|---|

Box Size ($h^{-1}\mathrm{Mpc}$) | 6592 | 7200 | 10815 | 3150 |

Number of CDM particles | $4120^3$ | $6000^3$ | $7210^3$ | $6300^3$ |

Starting redshift | 23 | 32 | 27 | 100 |

Initial power spectrum generator | Eisenstein & Hu (1998) | CAMB Source | CAMB Source | CAMB Source |

Initial displacement | Zel'dovich | Zel'dovich | Zel'dovich | 2LPT |

## Outputs from the simulation

- Snapshot data at z= 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 1, and 4
- All-sky past lightcone data out to z=1.5
- Merger trees of FoF halos from z = 16 to 0, with their gravitationally most bound member particles

## Computers used

- TACHYONII:
SUN Blades B6275 at KISTI
- System resources used for the simulation(HR2/HR3)
- 1000/1030 nodes
- 8000/8240 CPU cores
- 9/21 TB main memory
- Infiniband interconnection
- about 200/400 TB disk storage of Lustre Filesystem
- total 20 days in wallclock time

- QUEST: Linux Cluster at KIAS
- System resources used for the analysis
- 64 nodes
- 256 CPU cores
- 512 GB main memory
- Myrinet interconnection
- about 640 TB disk storage