High energy neutrinos produced in the accretion disks by neutrons from nuclei disintegrated in the AGN jets

TL;DR

This paper models how accelerated nuclei in AGN jets produce neutrons that cascade in accretion disks, generating neutrinos that could explain the extragalactic neutrino background observed by IceCube.

Contribution

It introduces a novel mechanism for neutrino production involving neutron cascades in accretion disks of AGNs, linking jet physics to neutrino background.

Findings

Neutrons from jet-accelerated nuclei can produce detectable neutrino spectra.

The model can account for the IceCube extragalactic neutrino background.

Neutrino signals from nearby radio galaxies are likely undetectable.

Abstract

We investigate the consequences of acceleration of nuclei in jets of active galaxies not far from the surface of an accretion disk. The nuclei can be accelerated in the re-connection regions in the jet and/or at the jet boundary, between the relativistic jet and its cocoon. It is shown that the relativistic nuclei can efficiently fragment onto specific nucleons in collisions with the disk radiation. Neutrons, directed towards the accretion disk, take a significant part of energy from the relativistic nuclei. These neutrons develop a cascade in the dense accretion disk. We calculate the neutrino spectra produced in such hadronic cascade within the accretion disk. We propose that the neutrinos produced in such scenario from the whole population of super-massive black holes in active galaxies can explain the extragalactic neutrino background recently measured by the IceCube neutrino detector, provided that $5\%$ fraction of galaxies is AGN and a few percent of neutrons reach the accretion disk. It is predicted that the neutrino signals in the present neutrino detectors, produced in terms of such a model, are not expected to be detectable even from the nearby radio galaxies similar to M87.