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

Abstract

We present a comparison of major methodologies of fast generating mock halo or galaxy catalogues. The comparison is done for two-point (power spectrum and 2-point correlation function in real-and redshift-space), and the three-point clustering statistics (bispectrum and 3-point correlation function). The reference catalogues are drawn from the BigMultiDark Nbody simulation. Both friend-of-friends (including distinct halos only) and spherical overdensity (including distinct halos and subhalos) catalogues 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 h −1 Mpc or k > 0.15 h Mpc −1 . Full N -body solutions will remain indispensable to produce reference catalogues. Nevertheless, we have demonstrated that the more efficient approximate solvers can reach a few percent accuracy in terms of clustering statistics at the scales interesting for

Comparing approximate methods for mock catalogues and covariance matrices – III: bispectrum

“…These considerations have been already illustrated by the results of the code-comparison project of Chuang et al (2015b). This work comprises a comparison of both the 3-Point Correlation Function and the bispectrum of halos of minimal mass of 10 13 h −1 M , very similar to one of the two samples considered in our work, but evaluated at the lower redshift z 0.55.…”

The accuracy of weak lensing simulations

“…The code comparison we present in this paper adds to a large body of work on the validation of numerical N -body codes and algorithms to extract cosmological information from their output. Some of the codes/methods already subject to similar testing include: gravity-only N -body algorithms (Schneider et al 2016), including non-standard gravity (Winther et al 2015), galaxy formation codes (Scannapieco et al 2012), methods to identify halos/subhalos (Knebe et al 2011;Onions et al 2012), galaxies (Knebe et al 2013), voids (Colberg et al 2008) and tidal debris (Elahi et al 2013) from the output of N -body simulations, codes to construct halo merger trees (Srisawat et al 2013) and fast generation of halo catalogues (Chuang et al 2015), including comparing the covariances of their two- (Lippich et al 2019;Blot et al 2019) and three-point statistics (Colavincenzo et al 2019). The importance of validation analyses such as these is crucial to identify and mitigate sources of systematic errors in our theoretical predictions.…”

Comparing approximate methods for mock catalogues and covariance matrices – I. Correlation function

“…The nIFTy comparison project by Chuang et al (2015) presented a detailed comparison of major approximate methods regarding their ability to reproduce clustering statistics (two-point correlation function, power spectrum and bispectrum) of halo samples drawn out of N-body simulations. Here we take the comparison of different approximate methods one step further.…”