ICE-COLA: fast simulations for weak lensing observables

TL;DR

ICE-COLA is an efficient approximate simulation method that accurately models weak lensing observables and halo catalogues, enabling fast generation of mock data for upcoming galaxy surveys.

Contribution

This paper extends ICE-COLA to produce weak lensing maps and halo catalogues in the light cone, demonstrating high accuracy beyond non-linear scales compared to full N-body simulations.

Findings

Convergence power spectra agree within 1% up to high multipoles for sources at z=1.

Shear two-point functions are accurate down to a few arcminutes.

The method remains stable with increased angular resolution.

Abstract

Approximate methods to full N-body simulations provide a fast and accurate solution to the development of mock catalogues for the modeling of galaxy clustering observables. In this paper we extend ICE-COLA (Izard et al. 2016), based on an optimized implementation of the approximate COLA method, to produce weak lensing maps and halo catalogues in the light cone using an integrated and self consistent approach. We show that despite the approximate dynamics, the catalogues thus produced enable an accurate modeling of weak lensing observables one decade beyond the characteristic scale where the growth becomes non-linear. In particular, we compare ICE-COLA to the MICE-GC N-body simulation for some fiducial cases representative of upcoming surveys and find that, for sources at redshift $z=1$, their convergence power spectra agree to within one percent up to high multipoles (i.e., of order $1000$). The corresponding shear two point functions, $\xi_{+}$ and $\xi_{-}$, yield similar accuracy down to $2$ and $20$ arcmin respectively, while tangential shear around a $z=0.5$ lens sample is accurate down to $4$ arcmin. We show that such accuracy is stable against an increased angular resolution of the weak lensing maps. Hence, this opens the possibility of using approximate methods for the joint modeling of galaxy clustering and weak lensing observables and their covariance in ongoing and future galaxy surveys.