Hadronuclear interactions in AGN jets as the origin of the diffuse high-energy neutrino background

TL;DR

This paper investigates how hadronuclear interactions in AGN jets could explain the diffuse high-energy neutrino background observed by IceCube, considering different jet orientations and gamma-ray transparency.

Contribution

It models neutrino and gamma-ray fluxes from AGN jets based on their luminosity function and beaming patterns, providing new insights into their roles in high-energy neutrino production.

Findings

Blazar jets with opaque gamma-ray regions can explain PeV neutrino background.

Radio galaxy jets with large viewing angles can account for TeV neutrino background.

Only blazars can potentially explain the diffuse neutrino background around PeV energies.

Abstract

The origin of diffuse high-energy neutrinos from TeV to PeV energies detected by IceCube Observatory remains a mystery. In our previous work, we have shown that hadronuclear (p-p) interactions in AGN jets could be important and generate detectable very-high-energy emissions. Here, we further explore these interactions in the AGN jets based on their luminosity function. The diffuse neutrino flux and corresponding $\gamma$-ray flux have been calculated and compared with observational data. In our modeling, two beaming patterns are considered separately. To make sure that the corresponding $\gamma$-ray flux does not overshoot the diffuse $\gamma$-ray background, we find that if the neutrino production region in jet is opaque to $\gamma$ rays, p-p interactions in AGN jets with a small viewing angle (the blazar case) are able to interpret the PeV neutrino background. Similarly, AGN jets with a large viewing angle (the radio galaxy case) may interpret the TeV neutrino background. While, if the neutrino production region is transparent to $\gamma$ rays, only blazars have the potential to interpret the DNB around PeV band. Some caveats are also discussed.