The shape of the extragalactic cosmic ray spectrum from Galaxy Clusters

TL;DR

This paper investigates how cosmic rays escape from galaxy clusters and how interactions within the clusters suppress the flux, affecting the observed extragalactic cosmic ray spectrum and composition at ultra-high energies.

Contribution

It provides a detailed analysis of cosmic ray confinement, escape, and attenuation in galaxy clusters, highlighting their impact on the observed spectrum and composition.

Findings

Suppression of cosmic ray flux due to confinement times comparable to source age.

Significant attenuation of heavy nuclei flux from interactions within clusters.

Implications for interpreting ultra-high-energy cosmic ray composition data.

Abstract

We study the diffusive escape of cosmic rays from a central source inside a galaxy cluster to obtain the suppression in the outgoing flux appearing when the confinement times get comparable or larger than the age of the sources. We also discuss the attenuation of the flux due to the interactions of the cosmic rays with the cluster medium, which can be sizeable for heavy nuclei. The overall suppression in the total cosmic ray flux expected on Earth is important to understand the shape of the extragalactic contribution to the cosmic ray spectrum for $E/Z<1$ EeV. This suppression can also be relevant to interpret the results of fits to composition-sensitive observables measured at ultra-high energies.