TANAMI counterparts to IceCube high-energy neutrino events

TL;DR

This paper investigates the potential astrophysical sources of IceCube high-energy neutrino events by analyzing AGN counterparts, especially blazars, using multiwavelength data and spectral modeling to estimate their neutrino emission contributions.

Contribution

It presents a multiwavelength spectral analysis of AGN coincident with IceCube neutrino events and estimates their cumulative neutrino flux contribution, highlighting blazars as plausible sources.

Findings

Blazars' integrated emission can explain some IceCube neutrino events.

Faint unresolved blazars contribute significantly to the neutrino flux.

Individual blazars are unlikely to produce the observed neutrino energies alone.

Abstract

Since the discovery of a neutrino flux in excess of the atmospheric background by the IceCube Collaboration, searches for the astrophysical sources have been ongoing. Due to the steeply falling background towards higher energies, the PeV events detected in three years of IceCube data are the most likely ones to be of extraterrestrial origin. Even excluding the PeV events detected so far, the neutrino flux is well above the atmospheric background, so it is likely that a number of sub-PeV events originate from the same astrophysical sources that produce the PeV events. We study the high-energy properties of AGN that are positionally coincident with the neutrino events from three years of IceCube data and show the results for event number 4. IC 4 is a event with a low angular error (7.1$^\circ$) and a large deposited energy of 165 TeV. We use multiwavelength data, including Fermi/LAT and X-ray data, to construct broadband spectra and present parametrizations of the broadband spectral energy distributions with logarithmic parabolas. Assuming the X-ray to {\gamma}-ray emission in blazars originates in the photoproduction of pions by accelerated protons, their predicted neutrino luminosity can be estimated. The measurements of the diffuse extragalactic background by Fermi/LAT gives us an estimate of the flux contributions from faint unresolved blazars. Their contribution increases the number of expected events by a factor of $\sim$2. We conclude that the detection of the IceCube neutrinos IC4, IC14, and IC20 can be explained by the integral emission of blazars, even though no individual source yields a sufficient energy output.