A Hadronic Scenario for the Galactic Ridge

TL;DR

This paper models the gamma-ray and neutrino emissions from the Galactic Ridge using a cosmic-ray transport scenario with spatially dependent diffusion, predicting signals that could explain IceCube observations and guiding future neutrino telescope searches.

Contribution

It introduces a hadronic model with spatially dependent diffusion to explain gamma-ray and neutrino emissions from the Galactic Ridge, aligning with recent observations.

Findings

The model predicts a harder neutrino spectrum than conventional models.

Predicted neutrino flux can account for a significant fraction of IceCube's astrophysical flux.

Future telescopes like KM3NeT can effectively observe the Galactic Ridge neutrino emission.

Abstract

Several observations from Fermi-LAT, up to few hundred GeV, and from H.E.S.S., up to $\sim$ 10 TeV, reported an intense $\gamma$-ray emission from the inner part of the Galactic plane. After the subtraction of point-like contributions, the remaining $\gamma$-ray spectrum can provide important hints about the cosmic-ray (CR) population in that region. In particular, the diffuse spectrum measured by both Fermi-LAT and H.E.S.S. in the Galactic Ridge is significantly harder with respect to the rest of the Galaxy. These results were recently interpreted in terms of a comprehensive CR transport model which, adopting a spatial dependent diffusion coefficient and convective velocity, reproduces Fermi-LAT results on the whole sky as well as local CR spectra. We showed as that model predicts a significantly harder neutrino diffuse emission compared to conventional scenarios: The predicted signal is able to account for a significant fraction of the astrophysical flux measured by IceCube. In this contribution, we use the same setup to calculate the expected neutrino flux from several windows in the inner Galactic plane and compare the results with IceCube observations and the sensitivities of Mediterranean neutrino telescopes. In particular, for the ANTARES experiment, we compare the model expectations with the upper limits obtained from a recent unblinded data-analysis focused on the galactic ridge region. Moreover, we also show the expectations from the galactic ridge for the future KM3NeT observatory, whose position is optimal to observe this portion of the sky.