Gamma-ray and neutrino diffuse emissions of the Galaxy above the TeV

TL;DR

This paper presents a spatially-dependent cosmic-ray diffusion model that explains gamma-ray and neutrino emissions in the Galaxy, successfully matching observations from Fermi-LAT, MILAGRO, H.E.S.S., and IceCube at various energies.

Contribution

The study introduces a novel diffusion model with spatial-dependent rigidity scaling that unifies gamma-ray and neutrino emission predictions across multiple experiments.

Findings

Model reproduces Fermi-LAT gamma-ray data and local cosmic-ray measurements.

Extrapolation matches MILAGRO and H.E.S.S. gamma-ray observations at TeV energies.

Predicts neutrino flux consistent with IceCube measurements above 25 TeV.

Abstract

As recently shown, Fermi-LAT measurements of the diffuse gamma-ray emission from the Galaxy favor the presence of a smooth softening in the primary cosmic-ray spectrum with increasing Galactocentric distance. This result can be interpreted in terms of a spatial-dependent rigidity scaling of the diffusion coefficient. The DRAGON code was used to build a model based on such feature. That scenario correctly reproduces the latest Fermi-LAT results as well as local cosmic-ray measurements from PAMELA, AMS-02 and CREAM. Here we show that the model, if extrapolated at larger energies, grasps both the gamma-ray flux measured by MILAGRO at 15 TeV and the H.E.S.S. data from the Galactic ridge, assuming that the cosmic-ray spectral hardening found by those experiments at about 250 GeV/n is present in the whole inner Galactic plane region. Moreover, we show as that model also predicts a neutrino emission which may account for a significant fraction, as well as for the correct spectral shape, of the astrophysical flux measured by IceCube above 25 TeV.