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We compare the full-sky morphology of the 511 keV gamma ray excess measuredby the INTEGRAL/SPI experiment to predictions of models based on dark matter(DM) scatterings that produce low-energy positrons: either MeV-scale DM thatannihilates directly into e+e- pairs, or heavy DM that inelastically scattersinto an excited state (XDM) followed by decay into e+e- and the ground state.Bydirect comparison to the data, we find that such explanations are consistentwith dark matter halo profiles predicted by numerical many-body simulations fora Milky Way-like galaxy. Our results favor an Einasto profile over the cuspierNFW distribution and exclude decaying dark matter scenarios whose predictedspatial distribution is too broad. We obtain a good fit to the shape of thesignal using six fewer degrees of freedom than previous empirical fits to the511 keV data. We find that the ratio of flux at Earth from the galactic bulgeto that of the disk is between 1.9 and 2.4, taking into account that 73% of thedisk contribution may be attributed to the beta decay of radioactive 26Al.

Interacting dark matter contribution to the Galactic 511 keV gamma ray emission: constraining the morphology with INTEGRAL/SPI observations