The Status of the Galactic Center Gamma-Ray Excess

TL;DR

The paper reviews the characteristics of the Galactic Center Gamma-Ray Excess, highlighting recent evidence that supports its origin from annihilating dark matter rather than unresolved pulsars.

Contribution

It summarizes recent findings that challenge previous pulsar-based interpretations and strengthen the dark matter annihilation hypothesis for the gamma-ray excess.

Findings

The excess has a spectrum consistent with 50 GeV dark matter particles.

It shows no small-scale clustering, contradicting pulsar population models.

The distribution is approximately spherical, not aligned with stellar populations.

Abstract

The Galactic Center Gamma-Ray Excess has a spectrum, angular distribution, and overall intensity that agree remarkably well with that expected from annihilating dark matter particles in the form of a $m_X \sim 50 \, {\rm GeV}$ thermal relic. Previous claims that these photons are clustered on small angular scales or trace the distribution of known stellar populations once appeared to favor interpretations in which this signal originates from a large population of unresolved millisecond pulsars. More recent work, however, has overturned these conclusions, finding that the observed gamma-ray excess does {\it not} contain discernible small scale power, and is distributed with approximate spherical symmetry, not tracing any known stellar populations. In light of these results, it now appears significantly more likely that the Galactic Center Gamma-Ray Excess is produced by annihilating dark matter.