Multi-wavelength emissions from dark matter annihilation processes in galaxy clusters using cosmological simulations

Mekuria, Remudin Reshid
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Based on the Marenostrum-MultiDark Simulation of galaxy Clusters (MUSIC) we develop semi-analytical models which provide multi-wavelength emission maps generated by dark matter (DM) annihilation processes in galaxy clusters and their sub-halos. We focus on radio and gamma-ray emission maps from neutralino DM annihilation processes testing two different neutralino masses, Mx = 35 GeV and 60 GeV along with two different models of the magnetic elds. A comparison of the radio ux densities from our DM annihilation model with the observed difuse radio emission from the Coma cluster shows that they are of the same order of magnitude. We determine the DM densities with a Smoothed Particle Hydrodynamics (SPH) kernel. This enables us to integrate the DM annihilation signal along any given line-of-sight through the volume of the cluster. In particular it allows us to investigate the contribution of sub-halos to the DM annihilation signal with very high resolution. Zooming in on a subset of high mass-to-light ratio (M/L) DM sub-halos, i.e. DM sub-halos with very low baryon content, we demonstrate that such targets can generate prominent annihilation signals. The radial distribution of high M/L DM sub-halos is more strongly peaked at R200crit = 1 compared to the distribution of all sub-halos which may suggest that the search for DM annihilation signals from sub-halos in clusters is most promising at R200crit. The radio ux densities from DM sub-halos are well within the sensitivity limit of the Square Kilometer Array (SKA) with an integration time of 1000 hours, and unlike clusters their gamma-ray spectrum is seen to be dominated by pion decay over a wide range of gamma-ray energies. Our model makes clear predictions for future radio and gamma-ray observations of the DM annihilation signals in clusters and their sub-halos.
A thesis submitted in ful lment of the requirements for the degree of Doctor of Philosophy in the School of Physics July 2017.
Mekuria, Remudin Reshid (2017) Multi-wavelength emissions from dark matter annihilation processes in galaxy clusters using cosmological simulations, University of the Witwatersrand, Johannesburg, <>