High-Energy Gamma Rays and Neutrinos from Nearby Radio Galaxies
  Multi-messenger data suggest that radio galaxies (i.e. non-blazar active
galaxies) are perhaps the most likely class of sources for the diffuse flux of
high-energy neutrinos reported by the IceCube Collaboration. In this study, we
consider the gamma-ray spectrum observed from four nearby radio galaxies
(Centaurus A, PKS 0625-35, NGC 1275 and IC 310) and constrain the intensity and
spectral shape of the emission injected from these sources, accounting for the
effects of attenuation and contributions from electromagnetic cascades
(initiated both within the radio galaxy itself and during extragalactic
propagation). Assuming that this gamma-ray emission is generated primarily
through the interactions of cosmic-ray protons with gas, we calculate the
neutrino flux predicted from each of these sources. Although this scenario is
consistent with the constraints published by the IceCube and ANTARES
Collaborations, the predicted fluxes consistently fall within an order of
magnitude of the current point source sensitivity. The prospects appear very
encouraging for the future detection of neutrino emission from the nearest
radio galaxies.
