On the Neutrino and Gamma-Ray Emission from NGC 1068

TL;DR

This paper models the neutrino and gamma-ray emissions from NGC 1068, linking the observed neutrinos to proton acceleration in the dense corona, and analyzes Fermi-LAT data to support the model.

Contribution

It presents a comprehensive physical model connecting neutrino and gamma-ray emissions from NGC 1068, including detailed processes and new data analysis.

Findings

Neutrinos are likely produced in the dense corona around the black hole.

Gamma-ray emission below 1 GeV is bright and consistent with the model.

High magnetic fields (B ≥ 6 kG) are required to match observations.

Abstract

IceCube has recently reported the detection of $\sim 1-10 \,{\rm TeV}$ neutrinos from the nearby active galaxy, NGC 1068. The lack of TeV-scale emission from this source suggests that these neutrinos are generated in the dense corona that surrounds NGC 1068's supermassive black hole. In this paper, we present a physical model for this source, including the processes of pair production, pion production, synchrotron, and inverse Compton scattering. We have also performed a new analysis of Fermi-LAT data from the direction of NGC 1068, finding that the gamma-ray emission from this source is very soft but bright at energies below $\sim 1 \, {\rm GeV}$. Our model can predict a gamma-ray spectrum that is consistent with Fermi-LAT observations, but only if the magnetic field within the corona of this active galactic nucleus (AGN) is quite high, namely $B\gtrsim 6 \, {\rm kG}$. To explain the observed neutrino emission, this source must accelerate protons with a total power that is comparable to its intrinsic X-ray luminosity. In this context, we consider two additional nearby active galaxies, NGC 4151 and NGC 3079, which have been identified as promising targets for IceCube.