Modelling injection and feedback of Cosmic Rays in grid-based cosmological simulations: effects on cluster outskirts

TL;DR

This paper introduces a new numerical scheme in the ENZO code to model cosmic ray injection, advection, and feedback in cosmological simulations, revealing significant effects on galaxy cluster properties.

Contribution

The paper presents a novel implementation of cosmic ray physics in an adaptive mesh refinement code, enabling detailed study of CR effects on cluster outskirts.

Findings

CR feedback decreases central gas density in clusters.

CRs reduce X-ray and SZ signals at the cluster center.

CRs increase gas density near the virial radius.

Abstract

We present a numerical scheme, implemented in the cosmological adaptive mesh refinement code ENZO, to model the injection of Cosmic Ray (CR) particles at shocks, their advection and their dynamical feedback on thermal baryonic gas. We give a description of the algorithms and show their tests against analytical and idealized one-dimensional problems. Our implementation is able to track the injection of CR energy, the spatial advection of CR energy and its feedback on the thermal gas in run-time. This method is applied to study CR acceleration and evolution in cosmological volumes, with both fixed and variable mesh resolution. We compare the properties of galaxy clusters with and without CRs, for a sample of high-resolution clusters with different dynamical states. At variance with similar simulations based on Smoothed Particles Hydrodynamics, we report that the inclusion of CR feedback in our method decreases the central gas density in clusters, thus reducing the X-ray and Sunyaev-Zeldovich effect from the clusters centre, while enhancing the gas density and its related observables near the virial radius.