The diffuse neutrino flux from the inner Galaxy: constraints from very high energy gamma-ray observations

TL;DR

This paper estimates the maximum possible neutrino flux from the inner Galaxy based on gamma-ray observations, suggesting that a km$^3$ detector could detect it, confirming the hadronic origin of the gamma-ray emission.

Contribution

It provides the first estimate of the maximum diffuse neutrino flux from the inner Galaxy constrained by gamma-ray data, assuming hadronic origin.

Findings

Maximum neutrino flux is compatible with gamma-ray observations.

A km$^3$ detector could detect the neutrino flux if near the maximum level.

Detection would confirm the hadronic origin of gamma-ray emission.

Abstract

Recently, the MILAGRO collaboration reported on the detection of a diffuse multi-TeV emission from a region of the Galactic disk close to the inner Galaxy. The emission is in excess of what is predicted by conventional models for cosmic ray propagation, which are tuned to reproduce the spectrum of cosmic rays observed locally. By assuming that the excess detected by MILAGRO is of hadronic origin and that it is representative for the whole inner Galactic region, we estimate the expected diffuse flux of neutrinos from a region of the Galactic disk with coordinates $-40^{\circ} < l < 40^{\circ}$. Our estimate has to be considered as the maximal expected neutrino flux compatible with all the available gamma ray data, since any leptonic contribution to the observed gamma-ray emission would lower the neutrino flux. The diffuse flux of neutrinos, if close to the maximum allowed level, may be detected by a km$^3$--scale detector located in the northern hemisphere. A detection would unambiguously reveal the hadronic origin of the diffuse gamma-ray emission.