High-energy neutrino astronomy - A probe of galactic nuclei

The powerful infrared emission from active galactic nuclei may be driven, directly or indirectly, by nonthermal processes, in which case the power of high-energy particle production may be as high as the IR luminosity. The nuclei of active galaxies contain, on various scales, enough matter to stop high-energy protons before they diffuse out of the nuclear region via pion-producing collisions. Thus the luminosity of the nucleus in high-energy neutrinos (at least about 1 TeV) (the primary decay product of charged pions) may in turn be comparable to the total power radiated by the nucleus. If such a hypothesis is true, then many active galactic nuclei may be detectable as point sources in high-energy neutrinos with the neutrino 'telescopes' that are being discussed. The overall cosmic neutrino background due to active galaxies may be orders of magnitude above the detection threshold.