Fermi-LAT Galactic Center Excess morphology of dark matter in simulations of the Milky Way galaxy

TL;DR

This paper investigates the shape of the gamma-ray excess at the Galactic Center, comparing dark matter annihilation predictions with astrophysical sources, using Milky Way-like galaxy simulations to inform future observational strategies.

Contribution

It introduces a novel analysis of the gamma-ray morphology based on Milky Way-like galaxy simulations, highlighting non-spherical dark matter distribution implications.

Findings

Dark matter models predict a non-spherical gamma-ray morphology.

Milky Way's merger history influences dark matter distribution shape.

Future telescopes can differentiate between dark matter and pulsar explanations.

Abstract

The strongest experimental evidence for dark matter is the Galactic Center gamma-ray excess observed by the Fermi telescope and even predicted prior to discovery as a potential dark matter signature via WIMP dark matter self-annihilations. However, an equally compelling explanation of the excess gamma-ray flux appeals to a population of old millisecond pulsars that also accounts for the observed boxy morphology inferred from the bulge old star population. We employ a set of Milky Way-like galaxies found in the Hestia constrained simulations of the local universe to explore the rich morphology of the central dark matter distribution, motivated by the GAIA discovery of a vigorous early merging history of the Milky Way galaxy. We predict a significantly non-spherical gamma-ray morphology from the WIMP interpretation. Future experiments, such as the Cherenkov Telescope Array, that extend to higher energies, should distinguish between the competing interpretations.