Fermi Bubbles under Dark Matter Scrutiny. Part I: Astrophysical Analysis

TL;DR

This paper analyzes Fermi bubbles' gamma-ray spectrum to explore potential dark matter signals, finding evidence of an excess at low latitudes compatible with dark matter annihilation and setting new upper limits on the annihilation cross section.

Contribution

It provides the first detailed spectral analysis of Fermi bubbles across latitudes, identifying a potential dark matter signature at low latitudes and constraining dark matter properties.

Findings

Detection of a gamma-ray excess at 1-4 GeV compatible with dark matter annihilation

Best-fit dark matter particle mass around 62 GeV

New upper limits on dark matter annihilation cross section

Abstract

The quest for Dark Matter signals in the gamma-ray sky is one of the most intriguing and exciting challenges in astrophysics. In this paper we perform the analysis of the energy spectrum of the \textit{Fermi bubbles} at different latitudes, making use of the gamma-ray data collected by the Fermi Large Area Telescope. By exploring various setups for the full-sky analysis we achieve stable results in all the analyzed latitudes. At high latitude, $|b|=20^{\circ}-50^{\circ}$, the \textit{Fermi bubbles} energy spectrum can be reproduced by gamma-ray photons generated by inverse Compton scattering processes, assuming the existence of a population of high-energy electrons. At low latitude, $|b|=10^{\circ}-20^{\circ}$, the presence of a bump at $E_{\gamma}\sim 1-4$ GeV, reveals the existence of an extra component compatible with Dark Matter annihilation. Our best-fit candidate corresponds to annihilation into $b\bar{b}$ with mass $M_{\rm DM}= 61.8^{+6.9}_{-4.9}$ GeV and cross section $<\sigma v> = 3.30^{+0.69}_{-0.49}\times 10^{-26}$ cm$^{3}$s$^{-1}$. In addition, using the energy spectrum of the \textit{Fermi bubbles}, we derive new conservative but stringent upper limits on the Dark Matter annihilation cross section.