Hard Cosmic Ray Sea in the Galactic Center: a consistent 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 by combining Fermi-LAT and H.E.S.S. data with a modified cosmic ray transport model, suggesting a harder diffusion coefficient and a less prominent PeVatron presence.

Contribution

It introduces a consistent model explaining gamma-ray emissions using a harder CR diffusion scaling and updated data analysis, challenging previous PeVatron evidence.

Findings

Gamma-ray emission explained by diffuse CR interactions with gas in the Galactic ridge.

Harder CR diffusion coefficient better fits the observed spectral index radial dependence.

Weaker evidence for a Galactic Center PeVatron compared to previous softer CR models.

Abstract

We present a novel interpretation of the gamma-ray diffuse emission measured by H.E.S.S. in the Galactic Center (GC) region and the Galactic ridge. Our starting base is an updated analysis of PASS8 Fermi-LAT data, which allows to extend down to few GeV the spectra measured by H.E.S.S. and to infer the primary CR radial distribution above 100 GeV. We compare those results with a CR transport model assuming a harder scaling of the diffusion coefficient with rigidity in the inner Galaxy. Such a behavior reproduces the radial dependence of the CR spectral index recently inferred from Fermi-LAT measurements in the inner GP. We find that, in this scenario, the bulk of the Galactic ridge emission can be naturally explained by the interaction of the diffuse, steady-state Galactic CR sea interacting with the gas present in the Central molecular zone. The evidence of a GC PeVatron is significantly weaker than that inferred adopting a conventional (softer) CR sea.