An excess of excesses examined via dark matter radio emissions from galaxies

Abstract

Cosmic-ray and gamma-ray observations have yielded several notable excesses that often lend themselves to explanation by various dark matter annihilation/decay models. In particular, the AMS-02 anti-proton and positron excesses have continued to grow more robust with the collection of more data. This is supplemented by gamma-ray excesses in the Galactic Centre and a high-energy break in spectrum of electron/positron cosmic rays seen by DAMPE. In this work we carefully model the magnetic field environments of M31 and M33 and use this to estimate expected synchrotron emissions from electrons produced via dark matter annihilation. By comparing this to available radio data we review simplifying assumptions used previously for dark matter hunting in these environments and produce novel constraints that are capable of fully ruling out dark matter models proposed to accommodate all the aforementioned excesses barring that of DAMPE. However, we do show that significant constraints can be placed upon the DAMPE parameter space with M31 data. In addition to this we project SKA non-observation constraints for the Reticulum II and Triangulum II dwarf galaxies and find these have potential to rule out cosmic-ray and gamma-ray excess-producing models of dark matter, even when the most conservative assumptions are employed.