IceCube Neutrinos from Hadronically Powered Gamma-Ray Galaxies

Abstract

In this work we use a multi-messenger approach to determine if the high energy diffuse neutrino flux observed by the IceCube Observatory can originate from $\gamma$-ray sources powered by Cosmic Rays interactions with gas. Typical representatives of such sources are Starburst and Ultra-Luminous Infrared Galaxies. Using the three most recent calculations of the non-blazar contribution to the extragalactic $\gamma$-ray background measured by the Fermi-LAT collaboration, we find that a hard power-law spectrum with spectral index $\alpha \leq 2.12$ is compatible with all the estimations for the allowed contribution from non-blazar sources, within 1$\sigma$. Using such a spectrum we are able to interpret the IceCube results, showing that various classes of hadronically powered $\gamma$-ray galaxies can provide the dominant contribution to the astrophysical signal above 100 TeV and about half of the contribution to the energy flux between 10-100 TeV. With the addition of neutrinos from the Galactic plane, it is possible to saturate the IceCube signal at high energy. Our result shows that these sources are still well motivated candidates.Comment: Accepted for publication on JCA