Towards a realistic astrophysical interpretation of the gamma-ray Galactic center excess

TL;DR

This paper proposes that the gamma-ray excess observed in the Galactic center can be explained by cosmic-ray sources and diffusion processes, challenging the dark matter annihilation hypothesis with a comparable fit quality.

Contribution

It introduces a model based on cosmic-ray sources and diffusion to interpret the gamma-ray excess, providing an alternative to dark matter explanations with similar fit performance.

Findings

Cosmic-ray source model fits the gamma-ray data as well as dark matter models.

The analysis shows the goodness-of-fit for the cosmic-ray scenario is comparable to dark matter.

The model successfully reproduces gamma-ray profiles in the region of interest.

Abstract

A spherical-symmetric gamma-ray emission from the central region of the Galaxy has been recently identified in Fermi-LAT data, and initially associated to dark matter particle annihilations. Guided by the evidence for a high gas density in the inner kpc of the Galaxy correlated with a very large Supernova rate, and hence with ongoing cosmic-ray acceleration, we investigate instead the possibility of addressing this excess in terms of ordinary cosmic-ray sources and standard steady-state diffusion. We alter the source term, and consistently the correlated gamma-ray emissions, in the context of a template-fitting analysis. We focus on a region of interest (ROI) defined as: $|l|<20^{\circ}; \hspace{5mm} 2^{\circ}<|b|<20^{\circ},$ with $l$ and $b$ the Galactic longitude and latitude coordinates. We analyze in detail the overall goodness of the fit of our framework, and perform a detailed direct comparison against data examining profiles in different directions. Remarkably, the test statistic of the fit related to our scenario turns out to be as good as the Dark Matter one in the ROI here considered.