Impact of Galaxy Clusters on UHECR propagation

TL;DR

This paper explores how the magnetized environment of galaxy clusters affects the propagation of ultra-high-energy cosmic rays, revealing that clusters significantly influence UHECR fluxes and their potential as sources.

Contribution

It introduces a universal parametrization for UHECR fluxes escaping galaxy clusters, accounting for cluster mass, source position, and particle type, based on a modified Monte Carlo simulation.

Findings

Galaxy clusters are highly opaque to UHECR nuclei.

The environment significantly alters UHECR fluxes and propagation.

Massive nearby clusters play a key role in UHECR astronomy.

Abstract

Galaxy clusters are the universe's largest objects in the universe kept together by gravity. Most of their baryonic content is made of a magnetized diffuse plasma. We investigate the impact of such magnetized environment on ultra-high-energy-cosmic-ray (UHECR) propagation. The intracluster medium is described according to the self-similar assumption, in which the gas density and pressure profiles are fully determined by the cluster mass and redshift. The magnetic field is scaled to the thermal components of the intracluster medium under different assumptions. We model the propagation of UHECRs in the intracluster medium using a modified version of the Monte Carlo code {\it SimProp}, where hadronic processes and diffusion in the turbulent magnetic field are implemented. We provide a universal parametrization that approximates the UHECR fluxes escaping from the environment as a function of the most relevant quantities, such as the mass of the cluster, the position of the source with respect to the center of the cluster and the nature of the accelerated particles. We show that galaxy clusters are an opaque environment especially for UHECR nuclei. The role of the most massive nearby clusters in the context of the emerging UHECR astronomy is finally discussed.