Neutrino-emission from active galactic nuclei as a diagnostic tool

Abstract

AGN, active galactic nuclei, are luminous objects at cosmological distances, which have been reported as sources of high energy γ-rays. The emission is probably nonthermal radiation from relativistic jets belonging to the AGN. Earlier investigations of these processes have suggested that neutrinos are among the radiation products of the jets of AGN. Our calculation of the high energetic neutrino emission from the jets of AGN is based on a recently published model for γ-ray production by a collimated, relativistic blast wave [1]. In this scenario a strong electron-proton beam, the jet of the AGN, is assumed to move with bulk Lorenz factor Γ and to collide with ambient matter. In that process the beam sweeps up interstellar matter. It is important to note that the swept-up interstellar particles retain their relative velocities with respect to the jet plasma, but get isotropised in the jet rest frame by self-excited Alfénic turbulence, which leads to a deceleration of the beam because of momentum conservation. The spectral evolution of the energetic particles is determined by the interplay between the injection rate, i.e., the density of the interstellar medium, the energy losses from electromagnetic radiation, and diffusive escape. The neutrino production resulting from the proton-proton collisions in the highly relativistic plasma of the jet is calculated via pion and muon decay. γ-ray emission produced via π0 -decay and leptonic emission of secondary electrons has been discussed in [1]. Here we show that the resulting neutrino emission is strongly correlated with the simultaneously emitted γ-radiation.