On the GeV excess in the diffuse \gamma-ray emission towards the Galactic Center

TL;DR

This study confirms the GeV excess in diffuse gamma-ray emission near the Galactic Center using Fermi-LAT data, revealing a bipolar morphology that challenges dark matter explanations and suggests alternative sources.

Contribution

The paper provides a detailed morphological analysis showing the GeV excess has a bipolar structure, contradicting previous spherical assumptions and excluding dark matter as its primary source.

Findings

Confirmed the existence of the GeV excess in gamma-ray emission.

Discovered the excess has a bipolar rather than spherical morphology.

Spectrum is smoother with less distinct features than previously reported.

Abstract

The Fermi-LAT \gamma-ray data have been used to study the morphological and spectral features of the so-called GeV excess - a diffuse radiation component recently discovered towards the Galactic centre. We used the likelihood method to analyze Fermi-LAT data. Our study does confirm the existence of such an extra component in the diffuse \gamma-ray emission at GeV energies. Based on a detailed morphological analysis, a spatial template that fits the data best was generated and adopted. Using this template, the energy distribution of \gamma-rays was derived in the 0.3-30 GeV energy interval. The spectrum appeared to have less distinct ('bump'-like) structure than previous reported. We argue that the morphology of this radiation component has a bipolar rather than a spherically symmetric structure as has been assumed a priori in previous studies. This finding excludes the associations of the GeV excess with Dark Matter. We briefly discuss the radiation mechanisms and possible source populations that could be responsible for this new component of diffuse gamma radiation.