On The Origin of IceCube's PeV Neutrinos

TL;DR

This paper discusses the potential astrophysical origins of IceCube's PeV neutrino events, suggesting gamma-ray bursts as a likely source and analyzing why other sources are less probable.

Contribution

It proposes that PeV neutrinos are likely produced by photo-meson interactions in gamma-ray bursts, providing a specific astrophysical source explanation for IceCube's observations.

Findings

Gamma-ray bursts can produce PeV neutrinos matching IceCube events.

Active galactic nuclei are less likely sources due to higher energy thresholds.

Cosmogenic neutrinos peak at energies higher than observed by IceCube.

Abstract

The IceCube collaboration has recently reported the observation of two events with energies in excess of 1 PeV. While an atmospheric origin of these events cannot be ruled out at this time, this pair of showers may potentially represent the first observation of high-energy astrophysical neutrinos. In this paper, we argue that if these events are neutrino-induced, then the neutrinos are very likely to have been produced via photo-meson interactions taking place in the same class of astrophysical objects that are responsible for the acceleration of the $\sim$$10^{17}$ eV cosmic ray spectrum. Among the proposed sources of such cosmic rays, gamma-ray bursts stand out as particularly capable of generating PeV neutrinos at the level implied by IceCube's two events. In contrast, the radiation fields in typical active galactic nuclei models are likely dominated by lower energy (UV) photons, and thus feature higher energy thresholds for pion production, leading to neutrino spectra which peak at EeV rather than PeV energies (models with significant densities of x-ray emission, however, could evade this problem). Cosmogenic neutrinos generated from the propagation of ultra-high energy cosmic rays similarly peak at energies that are much higher than those of the events reported by IceCube.