Why Cosmic Voids Matter: Mitigation of Baryonic Physics

TL;DR

This study demonstrates that cosmic voids are minimally affected by baryonic physics, confirming their robustness as cosmological probes and providing insights into their properties using advanced hydrodynamical and dark-matter-only simulations.

Contribution

It provides the first high-resolution comparison of void properties in hydrodynamical and dark-matter-only simulations, showing their near-indistinguishability and robustness.

Findings

Void properties are mostly unaffected by baryonic physics.

Deviations in baryon and dark matter distributions are relevant for weak lensing.

Void profiles in different simulations are nearly identical, confirming their universality.

Abstract

We utilize the Magneticum suite of state-of-the-art hydrodynamical, as well as dark-matter-only simulations to investigate the effects of baryonic physics on cosmic voids in the highest-resolution study of its kind. This includes the size, shape and inner density distributions of voids, as well as their radial density and velocity profiles traced by halos, baryonic and cold dark matter particles. Our results reveal observationally insignificant effects that slightly increase with the inner densities of voids and are exclusively relevant on scales of only a few Mpc. Most notably, we identify deviations in the distributions of baryons and cold dark matter around halo-defined voids, relevant for weak lensing studies. In contrast, we find that voids identified in cold dark matter, as well as in halos of fixed tracer density exhibit nearly indistinguishable distributions and profiles between hydrodynamical and dark-matter-only simulations, consolidating the universality and robustness of the latter for comparisons of void statistics with observations in upcoming surveys. This corroborates that voids are the components of the cosmic web that are least affected by baryonic physics, further enhancing their use as cosmological probes.