M31 gamma-ray emission - a closer look at different explanations

Abstract

A new measurement of a spatially extended gamma-ray signal from the center of M31 was published recently (Ackermann et al. 2017, ApJ 836, 208), reporting that the emission broadly resembles the Galactic center excess (GCE) of the Milky Way (MW). In this contribution we discuss the possibilities that the signal originates from a population of millisecond pulsars (MSPs), or alternatively the annihilation of dark matter (DM) particles. As an astrophysical interpretation in terms of MSPs appears viable, we derive upper limits on the annihilation cross section in the bb/τ+τ−-channel of weakly interacting massive particles (WIMPs) in a mass range from 1 GeV to 10 TeV, taking into consideration different DM density profiles and including the effect of substructure and adiabatic contraction.