Lightcone Galaxy Catalog: Horizon Run 4 Simulation

Introduction

This is the lightcone mock galaxy catalogs in Horizon Run 4 simulation (Kim, Park, L'Huillier & Hong 2015) created by the most bound halo particle(MBP)-galaxy correspondence model (Hong, Park & Kim 2016).

Horizon Run 4 simulation is a cosmological N-body simulation with the following properties:

• Box size: (3,150 cMpc/h)³
• Number of matter particles: 6,300³
• Cosmology: WMAP 5-year ΛCDM cosmology; (Ω_m, Ω_Λ, h, σ₈, n_s) = (0.26, 0.74, 0.72, 0.79, 0.96)

Data

The entire full-sky lightcone data up to z = 1.5 is split with 52 subsamples with comoving distance. Each data file has a name as LC_[subsample number].hdf5. See this file for the range of comoving distance and redshift for each data file.

Each data file is written as HDF5 file format containing the following properties:

• x, y, z: Position in comoving coordinate (cMpc/h)
• vx, vy, vz: Peculiar velocity (km/s). User can use it to apply the redshift space distortion (RSD).
• mass: Mass of the galaxy (Msun/h; see the warning below)

Warnings

Galaxy Mass

Note that the mass of the galaxy is not the FoF halo mass, subhalo mass, or the stellar mass. It is a rather artificial mass-like quantity that you can use as a proxy of galaxy luminosity in a way that brighter galaxies have higher mass.

A typical example of using mass is to make a volume-limited galaxy sample up to a certain brightness threshold.

1. First, calculate the number density of galaxies with the same brightness threshold from the observation.
2. Next, find the minimum mass threshold from the mock galaxy catalog that gives the same galaxy number density.
3. Then select the galaxies whose mass is above the given threshold to make the mock volume-limited galaxy sample.

However, note that the above example assumes that the both completeness of observation up to a given brightness threshold and the correlation between the given types of brightness and halo/stellar mass are very high.

Possible Duplication at z > 0.6

Since the box size of the Horozin Run 4 simulation is 3150 Mpc/h, the maximum radius of a sphere that fits within the simulation box is 1575 Mpc/h, which corresponds to the comoving distance at z = 0.6. Lightcone volume with higher redshift should be made, therefore, by adopting periodic boundary condition.

Therefore, if you need to avoid such effect, you may need to either focus only on lower redshifts or use partial sky area.

If you have questions on the above issues, please contact Dr. Sungwook E. Hong.

References

Please cite the following references if you use the above mock galaxy catalog.

• Kim, J., Park, C., L'Huillier, B., & Hong, S.E. 2015, JKAS, 48, 213
• Hong, S.E., Park, C. & Kim, J. 2016, ApJ, 823, 103

If you have a question, please contact Dr. Sungwook E. Hong.