Modelling the large scale structure of the Universe as a function of cosmology and baryonic physics

TL;DR

This paper introduces a fast, accurate framework combining rescaling and baryonification techniques to model the Universe's large-scale structure, accounting for baryonic effects and various cosmologies, useful for cosmological data analysis.

Contribution

The authors develop an efficient, flexible method to simulate baryonic effects on the matter power spectrum across different cosmologies with minimal computational cost.

Findings

The model reproduces baryonic effects on the matter power spectrum to percent accuracy.

It can handle arbitrary baryonic models and cosmologies, including neutrinos and dark energy.

Baryonic physics marginally degrades cosmological constraints from weak lensing.

Abstract

We present and test a framework that models the three-dimensional distribution of mass in the Universe as a function of cosmological and astrophysical parameters. Our approach combines two different techniques: a rescaling algorithm that modifies the cosmology of gravity-only N-body simulations, and a baryonification algorithm which mimics the effects of astrophysical processes induced by baryons, such as star formation and AGN feedback. We show how this approach can accurately reproduce the effects of baryons on the matter power spectrum of various state-of-the-art hydro-dynamical simulations (EAGLE, Illustris, Illustris-TNG, Horizon-AGN, and OWLS,Cosmo-OWLS and BAHAMAS), to percent level from very large down to small, highly nonlinear scales, k= 5 h/Mpc, and from z=0 up to z=2. We highlight that, thanks to the heavy optimisation of the algorithms, we can obtain these predictions for arbitrary baryonic models and cosmology (including massive neutrinos and dynamical dark energy models) with an almost negligible CPU cost. Therefore, this approach is efficient enough for cosmological data analyses. With these tools in hand we explore the degeneracies between cosmological and astrophysical parameters in the nonlinear mass power spectrum. Our findings suggest that after marginalising over baryonic physics, cosmological constraints inferred from weak gravitational lensing should be moderately degraded.