Speaker
Description
The origin of diffuse neutrinos and $\gamma-$rays is uncertain, 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 follows 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 the natural sites for efficient CR acceleration. Our predicted $\gamma-$ray flux from the individual clusters lies well below the present upper limits of LHAASO.
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.
