Baryon effects on void statistics in the EAGLE simulation

TL;DR

This study investigates how baryonic physics influences cosmic void statistics in the EAGLE simulation, revealing that baryons slightly alter void counts and properties, but DM-only simulations are generally sufficient for modeling voids.

Contribution

It provides a detailed comparison of void properties in hydrodynamical and DM-only simulations, highlighting the impact of baryons and galaxy selection methods on void statistics.

Findings

DM-only simulations produce 24% more voids than hydrodynamical ones.

Galaxy selection method significantly affects void size and density profiles.

Baryons have minimal overall impact on void statistics.

Abstract

Cosmic voids are promising tools for cosmological tests due to their sensitivity to dark energy, modified gravity and alternative cosmological scenarios. Most previous studies in the literature of void properties use cosmological N-body simulations of dark matter (DM) particles that ignore the potential effect of baryonic physics. Using a spherical underdensity finder, we analyse voids using the mass field and subhalo tracers in the EAGLE simulations, which follow the evolution of galaxies in a $\rm{\Lambda}$ cold dark matter Universe with state-of-the-art subgrid models for baryonic processes in a $(100 \rm{cMpc})^3$ volume. We study the effect of baryons on void statistics by comparing results with DM-only simulations that use the same initial conditions as EAGLE. When identifying voids in the mass field, we find that a DM-only simulation produces 24 per cent more voids than a hydrodynamical one due to the action of galaxy feedback polluting void regions with hot gas, specially for small voids with $r_{\rm{void}} \le 10\ \rm{Mpc}$. We find that the way in which galaxy tracers are selected has a strong impact on the inferred void properties. Voids identified using galaxies selected by their stellar mass are larger and have cuspier density profiles than those identified by galaxies selected by their total mass. Overall, baryons have minimal effects on void statistics, as void properties are well captured by DM-only simulations, but it is important to account for how galaxies populate DM haloes to estimate the observational effect of different cosmological models on the statistics of voids.