High-Energy Neutrinos in Light of Fermi-LAT

The production of high-energy astrophysical neutrinos is tightly linked to the emission of hadronic gamma-rays. I will discuss the recent observation of TeV to PeV neutrinos by the IceCube Cherenkov telescope in the context of gamma-ray astronomy. The corresponding energy range of hadronic gamma-rays is not directly accessible by extragalactic gamma-ray astronomy due to interactions with cosmic radiation backgrounds. Nevertheless, the isotropic sub-TeV gamma-ray background observed by the Fermi Large Area Telescope (LAT) contains indirect information from secondary emission produced in electromagnetic cascades and constrains hadronic emission scenarios. On the other hand, observation of PeV gamma-rays would provide a smoking-gun signal for Galactic emission. In general, the cross-correlation of neutrino emission with (extended) Galactic and extragalactic gamma-ray sources will serve as the most sensitive probe for a future identification of neutrino sources.