On the impact of baryons on the halo mass function, bias, and cluster cosmology

TL;DR

This paper investigates how baryonic physics influence galaxy cluster statistics and their implications for cosmological parameter estimation, emphasizing the importance of accounting for these effects in future surveys.

Contribution

It demonstrates that baryonic effects can be effectively modeled as halo mass variations and highlights their significance for accurate cosmological inferences.

Findings

Baryonic effects can be recast as halo mass variations in simulations.

Neglecting baryons significantly biases cosmological parameter estimates.

Halo bias and mass function are indirectly affected by baryons.

Abstract

Luminous matter produces very energetic events, such as active galactic nuclei and supernova explosions, that significantly affect the internal regions of galaxy clusters. Although the current uncertainty in the effect of baryonic physics on cluster statistics is subdominant as compared to other systematics, the picture is likely to change soon as the amount of high-quality data is growing fast, urging the community to keep theoretical systematic uncertainties below the ever-growing statistical precision. In this paper, we study the effect of baryons on galaxy clusters, and their impact on the cosmological applications of clusters, using the Magneticum suite of cosmological hydrodynamical simulations. We show that the impact of baryons on the halo mass function can be recast in terms on a variation of the mass of the halos simulated with pure N-body, when baryonic effects are included. The halo mass function and halo bias are only indirectly affected. Finally, we demonstrate that neglecting baryonic effects on halos mass function and bias would significantly alter the inference of cosmological parameters from high-sensitivity next-generations surveys of galaxy clusters.