PeV neutrinos from intergalactic interactions of cosmic rays emitted by active galactic nuclei

TL;DR

This paper proposes that cosmic ray interactions from active galactic nuclei produce high-energy gamma rays and neutrinos, explaining IceCube's PeV neutrino observations and suggesting AGNs accelerate protons to ultra-high energies.

Contribution

It introduces a model linking AGN-emitted cosmic rays to observed PeV neutrinos and gamma rays, highlighting the role of line-of-sight interactions in high-energy astrophysics.

Findings

Diffuse neutrino background consistent with IceCube data

Individual nearby sources cannot explain the neutrino flux

Active galactic nuclei can accelerate protons to EeV energies

Abstract

The observed very high energy spectra of distant blazars are well described by secondary gamma rays produced in line-of-sight interactions of cosmic rays with background photons. In the absence of the cosmic-ray contribution, one would not expect to observe very hard spectra from distant sources, but the cosmic ray interactions generate very high energy gamma rays relatively close to the observer, and they are not attenuated significantly. The same interactions of cosmic rays are expected to produce a flux of neutrinos with energies peaked around 1 PeV. We show that the diffuse isotropic neutrino background from many distant sources can be consistent with the neutrino events recently detected by the IceCube experiment. We also find that the flux from any individual nearby source is insufficient to account for these events. The narrow spectrum around 1 PeV implies that some active galactic nuclei can accelerate protons to EeV energies.