Decaying vs Annihilating Dark Matter in Light of a Tentative Gamma-Ray Line

TL;DR

This paper examines whether decaying or annihilating dark matter could explain a tentative gamma-ray line signal, analyzing constraints from various astrophysical observations and the spatial distribution of the excess.

Contribution

It compares the viability of decaying versus annihilating dark matter explanations for the gamma-ray line, considering multiple observational constraints and dark matter density profiles.

Findings

Higgsino and wino dark matter are excluded, even with nonthermal production.

Continuum gamma-ray flux constraints strongly limit annihilating dark matter models.

Decaying dark matter could explain the excess if there is an enhanced density near the Galactic center.

Abstract

Recently reported tentative evidence for a gamma-ray line in the Fermi-LAT data is of great potential interest for identifying the nature of dark matter. We compare the implications for decaying and annihilating dark matter taking the constraints from continuum gamma-rays, antiproton flux and morphology of the excess into account. We find that higgsino and wino dark matter are excluded, also for nonthermal production. Generically, the continuum gamma-ray flux severely constrains annihilating dark matter. Consistency of decaying dark matter with the spatial distribution of the Fermi-LAT excess would require an enhancement of the dark matter density near the Galactic center.