The Morphology of Exciting Dark Matter and the Galactic 511 keV Signal

TL;DR

This paper investigates how exciting dark matter could produce the Galactic 511 keV signal observed by INTEGRAL, analyzing its morphology and comparing it with data to assess its viability as an explanation.

Contribution

It provides the first full statistical analysis of exciting dark matter as a source of the 511 keV signal, demonstrating its better fit over annihilating dark matter models.

Findings

Exciting dark matter models fit the INTEGRAL data significantly better than annihilating dark matter.

The analysis covers dark matter masses from 100 GeV to 3 TeV and cross sections from 10^{-19} to 10^{-16} cm^3/s.

Exciting dark matter can improve the fit by Δχ^2 > 16 for most density profiles considered.

Abstract

We study the morphology of the 511 keV signal that could be produced by exciting dark matter (XDM) in the Milky Way. In this model, collisions between dark matter particles excite the dark matter to a state that can then decay back to the ground state, releasing an electron-positron pair. These electrons and positrons would then annihilate, producing 511 keV photons that could explain the 511 keV signal seen by INTEGRAL at the Galactic Center. We compare the resulting flux with the most recent INTEGRAL data, performing the first full statistical analysis of the exciting dark matter model. We focus on exciting dark matter in the mass and cross section ranges 100 GeV $\lesssim m_{\chi} \lesssim$ 3 TeV and $10^{-19}$ cm$^3$ s$^{-1} \lesssim \langle \sigma v \rangle \lesssim 10^{-16}$ cm$^3$ s$^{-1}$. We show that exciting dark matter can provide a significantly better fit than the simpler case of annihilating dark matter, with $\Delta\chi^2 > 16$ for all but one of the density profiles we consider.