On the morphology of $\gamma-$ray emission induced by $e^{\pm}$ from annihilating self-interacting dark matter

TL;DR

This paper models the morphology of gamma-ray emission from self-interacting dark matter annihilation, suggesting that inverse Compton scattering of electrons/positrons could explain the observed Galactic Center excess, with specific asymmetry features.

Contribution

It provides a detailed calculation of gamma-ray emission morphology from SIDM annihilation, highlighting the dominance of inverse Compton scattering and potential asymmetry signatures.

Findings

ICS dominates bremsstrahlung in gamma-ray production

Gamma-ray emission concentrates along the Galactic plane

Asymmetry degrees up to 0.3 are possible in certain regions

Abstract

With the Fermi-LAT data quite a few research groups have reported a spatially extended GeV $\gamma$-ray excess surrounding the Galactic Center (GC). The physical origin of such a GeV excess is still unclear and one interesting possibility is the inverse Compton scattering of the electrons/positrons from annihilation of self-interacting dark matter (SIDM) particles with the interstellar optical photons. In this work we calculate the morphology of such a kind of $\gamma$-ray emission. For the annihilation channel of $\bar{\chi}\chi\rightarrow \phi\phi\rightarrow e^{+}e^{-}e^{+}e^{-}$, the inverse Compton scattering (ICS) dominates over the bremsstrahlung on producing the GeV $\gamma$-ray emission. For the SIDM particles with a rest mass $m_\chi \sim $ tens GeV that may be favored by the modeling of the Galactic GeV excess, the ICS radiation at GeV energies concentrates along the Galactic plane. The degrees of asymmetry high up to $\geq 0.3$ are found in some regions of interest, which in turn proposes a plausible test on the SIDM interpretation of the GeV excess.