High-Energy Neutrino and Gamma Ray Production in Clusters of Galaxies

TL;DR

This paper models how galaxy clusters contribute to the diffuse neutrino and gamma-ray backgrounds by simulating cosmic ray interactions within their magnetized environments over cosmic time.

Contribution

It introduces a comprehensive 3D MHD simulation framework for cosmic ray propagation in galaxy clusters, accounting for their magnetic fields and cosmological evolution.

Findings

Clusters significantly contribute to the observed diffuse neutrino and gamma-ray fluxes.

Most contributions originate from massive clusters ($>10^{14} M_ ext{sun}$) at low redshift ($z<0.3$).

Cosmic rays with energies up to $10^{17}$ eV can be confined within clusters for cosmological timescales.

Abstract

We compute the contribution from clusters of galaxies to the diffuse neutrino and $\gamma-$ray background. Due to their unique magnetic-field configuration, cosmic rays (CRs) with energy $\leq10^{17}$ eV can be confined within these structures over cosmological time scales, and generate secondary particles, including neutrinos and $\gamma-$rays, through interactions with the background gas and photons. We employ three-dimensional (3D) cosmological magnetohydrodynamical (MHD) simulations of structure formation to model the turbulent intergalactic and intracluster media. We propagate CRs in these environments using multi-dimensional Monte Carlo simulations across different redshifts (from $z \sim 5$ to $z = 0$), considering all relevant photohadronic, photonuclear, and hadronuclear interactions. We also include the cosmological evolution of the CR sources. We find that for CRs injected with a spectral index $1.5 - 2.7$ and cutoff energy $E_\text{max} = 10^{16} - 10^{17}$~eV, clusters contribute to a substantial fraction to the diffuse fluxes observed by the IceCube and Fermi-LAT, and most of the contribution comes from clusters with $M > 10^{14} \, M_{\odot}$ and redshift $z < 0.3$. We also estimated the multimessenger contributions from the local galaxy cluster.