The THREEHUNDRED project: The effect of baryon processes at galaxy cluster scale

Weiguang Cui

doi:10.1051/epjconf/202225700011

Abstract

The role of baryon models in hydrodynamic simulations is still unclear. Future surveys that use cluster statistics to precisely constrain cosmological models require a better understanding of the baryonic effects. Using the hydro-simulated galaxy clusters from different baryon models (Gadget-MUSIC, Gadget-X and Gizmo-SIMBA) from the THREEHUNDRED project, we can address this question into more details. We find that the galaxy cluster mass change due to different baryon models is at a few per cent level. However, the mass changes can be positive or negative depending on the baryon models. Such a small mass change leaves a weak influence (slightly larger compared to the mass changes) on both the cumulative halo numbers and the differential halo mass function (HMF) above the mass completeness. Similarly to to the halo mass change, the halo mass or the HMF can be increased or decreased with respect to the dark-matter-only (DMO) run depending on the baryon models.

Highlights

More than a decade ago, theoretical studies on structure and galaxy formations were relying N-body DMO simulations, see the well-known Millennium simulations [1] and the MultiDark simulations [2], for example
Limited by the current computation power, unknown baryon processes or incomplete baryon models implemented in the simulation codes [see 4, for the current development of baryon models in hydrodynamic simulations] as well as the dependence on the simulation resolution[5], we are still facing difficulties to fully model galaxy formation at the non-linear scales
The THREEHUNDRED project [9] is a re-simulation of 324 most massive galaxy clusters (Mvir > 8 × 1014 h−1M )1 from the MultiDark simulation (MDPL2, [2], referred to as the DMO run in this paper) which utilises the cosmological parameters from the Planck mission [10], and has a periodic cube of comoving length 1 h−1 Gpc containing 38403 DM particles with a mass of 1.5 × 109 h−1M

Summary

Introduction

More than a decade ago, theoretical studies on structure and galaxy formations were relying N-body DMO simulations, see the well-known Millennium simulations [1] and the MultiDark simulations [2], for example. As we can only directly observe the galaxies in the sky and simulations only contains gravitational bound objects – dark matter halos, there is a missing connection between observation – galaxies, and theoretical prediction – dark matter halos Numerous techniques, such as hydrodynamic simulations, semi-analytic models, empirical forward modelling, subhalo abundance modelling and halo occupation models (from more physical models to more empirical models), are developed to bridge this connection [see 3, for a recent review]. Theoretically understanding the cluster masses, especially their changes according to different baryon models, is essential to accurately constrain cosmology parameters [see 8, for a detailed discussion]. In this short article, we will address this question, focusing on the galaxy cluster scale with clusters simulated with different codes from the THREEHUNDREDproject[9].

The simulated galaxy clusters from the THREEHUNDRED project

The effects on halo mass and HMF

Findings

Conclusion and discussion