Evolution of Dark Matter Halos and their Radio Emissions

Abstract

Radio synchrotron emission is expected as a natural by-product of the self-annihilation of super-symmetric dark matter particles. In this work we discuss the general properties of the radio emission expected in a wide range of dark matter halos, from local dwarf spheroidal galaxies to large and distant galaxy clusters with the aim to determine the neutralino dark matter detection prospects of the Square Kilometre Array (SKA). The analysis of the SKA detection of dark matter(DM)-induced radio emission is presented for structures spanning a wide range of masses and redshifts, and we also analyze the limits that the SKA can set on the thermally averaged neutralino annihilation cross-section in the event of non-detection. To this aim, we construct a model of the redshift evolution of the radio emissions of dark matter halos and apply it to generate predicted fluxes from a range of neutralino masses and annihilation channels for the dark matter halos surrounding dwarf galaxies, galaxies and galaxy clusters. Using the available SKA performance predictions and its ability to determine an independent measure of the magnetic field in cosmic structures, we explore both the detailed detection prospects and the upper-bounds that might be placed on the neutralino annihilation cross-section in the event of non-detection. We find that the SKA can access a neutralino parameter space far larger than that of any preceding indirect-detection experiment, also improving on the realistic CTA detection prospects, with the possibility of setting cross-section upper-bounds up to four orders of magnitude below the thermal relic density bound. Additionally, we find that neutralino radio emissions carry redshift-independent signatures of the dominant annihilation channel and of neutralino mass, offering therefore a means to identify such non-thermal emissions within the observing frequency range of the SKA.