# Diffuse cosmic rays shining in the Galactic center: A novel interpretation of H.E.S.S. and Fermi-LAT gamma-ray data

## TL;DR

This paper offers a new interpretation of gamma-ray emissions in the Galactic center, suggesting they result from cosmic-ray interactions with gas, using data-driven analysis and a position-dependent diffusion model.

## Contribution

It introduces a novel cosmic-ray transport model with position-dependent diffusion that explains gamma-ray observations without requiring a central Pevatron source.

## Key findings

- Diffuse gamma-ray emission explained by cosmic-ray interactions with gas
- Radial dependence of cosmic-ray spectral index matches observations
- No definitive evidence for a central Pevatron source

## Abstract

We present a novel interpretation of the $\gamma$-ray diffuse emission measured by Fermi-LAT and H.E.S.S. in the Galactic center (GC) region and the Galactic ridge (GR). In the first part we perform a data-driven analysis based on PASS8 Fermi-LAT data: we extend down to few GeV the spectra measured by H.E.S.S. and infer the primary cosmic-ray (CR) radial distribution between 0.1 and 3 TeV. In the second part we adopt a CR transport model based on a position-dependent diffusion coefficient. Such behavior reproduces the radial dependence of the CR spectral index recently inferred from the Fermi-LAT observations. We find that the bulk of the GR emission can be naturally explained by the interaction of the diffuse steady-state Galactic CR sea with the gas present in the Central Molecular Zone. Although our results leave room for a residual radial-dependent emission associated with a central source, the relevance of the large-scale background prevents from a solid evidence of a GC Pevatron.