Abstract

Poster - Splinter MeVSky   (MW-0337)

Observations of the dark matter halo of the Andromeda Galaxy with INTEGRAL/SPI

Laura Eisenberger, Thomas Siegert
University of Wuerzburg

The Andromeda galaxy (M31) is a promising target for the indirect search of dark matter (DM) due to its proximity and expected massive DM halo. It functions as a test case for a Milky Way (MW) like galaxy as the isotropic emission from the MW halo itself cannot be detected with a coded mask telescope like INTEGRAL/SPI. MeV data can put strong limits on DM models from the MeV up to the TeV mass range since weakly interacting massive particles also produce a significant flux of secondary MeV photons from inverse Compton scattering and positron annihilation. We analyze the spectrum of M31 obtained with the SPI instrument to constrain DM models. From the 511 keV emission from positron annihilation, we estimate the pair production rate in M31 to derive a lower mass limit on thermal DM of 2 MeV in the case of subhalo boosting. We further constrain the DM annihilation and decay parameter space for the e⁺e⁻ channel, excluding velocity-averaged cross-sections down to 1e-25 cm³ s⁻¹ and decay lifetimes up to 1e25 s. We also place limits on the abundance of primordial black holes with masses below 1e17 g, based on their evaporation into photons and e⁺e⁻. With forthcoming missions like COSI, a coherent analysis, ranging from multi-galaxy studies to the cosmic gamma-ray background, promises to improve upon existing DM constraints by a factor of 10 in two years.