High-energy Multi-messenger Emission from Galaxy Clusters in the Local Universe

TL;DR

This study models the diffuse gamma-ray and neutrino emission from galaxy clusters using detailed simulations, finding fluxes below current observational limits and providing insights into cosmic-ray acceleration in clusters.

Contribution

It introduces a combined MHD and Monte Carlo simulation approach to predict gamma-ray and neutrino fluxes from galaxy clusters, incorporating physically motivated CR injection assumptions.

Findings

Predicted gamma-ray fluxes are below LHAASO upper limits.

Results are consistent with IceCube neutrino flux limits.

Fermi-LAT diffuse gamma-ray flux exceeds model predictions.

Abstract

The origin of diffuse neutrinos and $\gamma$-rays is unknown, and galaxy clusters hosting AGN and starburst galaxies are the most probable sources of these cosmic messengers. In this work, we investigate the diffuse $\gamma$-ray and neutrino emission from the Virgo, Perseus, and Coma clusters using a detailed numerical method, combining MHD simulations with Monte Carlo methods. The MHD simulation provides the distributions of temperature, gas, and magnetic field in clusters. The Monte Carlo simulations are used to investigate the cosmic-ray (CR) propagation in ICM and subsequently the secondaries stemming from CRs. Our primary assumption is that CR injection scales with the gas density of clusters, providing a physically motivated approximation. High-density regions in clusters are associated with strong turbulence and prominent shock structures, making them natural sites for efficient CR acceleration. Our predicted $\gamma$-ray flux from the individual clusters lies well below the present LHAASO upper limits. The MAGIC observations of the central source NGC $1275$ of the Perseus cluster are significantly higher than our results. Further, we estimated the cumulative $\gamma$-ray and neutrino fluxes from clusters with masses $\gtrsim 5\times 10^{13}, M_{\odot}$ in the local Universe (within $500$ Mpc). The diffuse $\gamma$-ray flux reported by the Fermi-LAT collaboration is significantly higher than our results. Our predictions are consistent with IceCube's existing upper limits on the unresolved neutrino flux from galaxy clusters ($M > 10^{14}, M_{\odot}$) up to $z = 2$.