nIFTy Cosmology: Galaxy/halo mock catalogue comparison project on clustering statistics

TL;DR

This paper compares various fast methods for generating mock galaxy and halo catalogues, showing that approximate solvers can achieve high accuracy in clustering statistics after calibration, aiding large-scale structure analysis.

Contribution

It evaluates the accuracy of different mock catalogue generation methods against N-body simulations for clustering statistics, highlighting the effectiveness of perturbation theory and semi-N-body approaches.

Findings

Perturbation-based models match N-body results well for most clustering statistics.

Semi-N-body methods achieve 1% accuracy for quadrupole at small scales.

Approximate solvers, after calibration, are useful for covariance studies and large parameter scans.

Abstract

We present a comparison of major methodologies of fast generating mock halo or galaxy catalogues. The comparison is done for two-point and the three-point clustering statistics. The reference catalogues are drawn from the BigMultiDark N-body simulation. Both friend-of-friends (including distinct halos only) and spherical overdensity (including distinct halos and subhalos) catalogs have been used with the typical number density of a large-volume galaxy surveys. We demonstrate that a proper biasing model is essential for reproducing the power spectrum at quasilinear and even smaller scales. With respect to various clustering statistics a methodology based on perturbation theory and a realistic biasing model leads to very good agreement with N-body simulations. However, for the quadrupole of the correlation function or the power spectrum, only the method based on semi-N-body simulation could reach high accuracy (1% level) at small scales, i.e., r<25 Mpc/h or k>0.15 h/Mpc. Full N-body solutions will remain indispensable to produce reference catalogues. Nevertheless, we have demonstrated that the far more efficient approximate solvers can reach a few percent accuracy in terms of clustering statistics at the scales interesting for the large-scale structure analysis after calibration with a few reference N-body calculations. This makes them useful for massive production aimed at covariance studies, to scan large parameter spaces, and to estimate uncertainties in data analysis techniques, such as baryon acoustic oscillation reconstruction, redshift distortion measurements, etc.