On the possible contributions of two nearby blazars to the NGC 4151 neutrino hotspot

TL;DR

This study models the potential neutrino emission from two nearby blazars to evaluate their contribution to the neutrino signal observed from NGC 4151, finding their impact is minor but detectable with future observatories.

Contribution

The paper presents a detailed spectral energy distribution modeling of two blazars and assesses their neutrino emission contribution to a nearby galaxy's neutrino hotspot.

Findings

Neutrino emission peaks at ~10^17 eV for both blazars.

Their contribution to the 10 TeV neutrino signal from NGC 4151 is minor.

Future radio-based neutrino telescopes could detect these sources.

Abstract

The origin of the high-energy astrophysical neutrinos discovered by IceCube remains unclear, with both blazars and Seyfert galaxies emerging as potential sources. Recently, the IceCube Collaboration reported a ${\sim}{3}\sigma$ neutrino signal from the direction of a nearby Seyfert galaxy NGC 4151. However, two gamma-ray loud BL Lac objects, 4FGL 1210.3+3928 and 4FGL J1211.6+3901, lie close to NGC 4151, at angular distances of 0.08$^\circ$ and 0.43$^\circ$, respectively. We investigate the potential contribution of these two blazars to the observed neutrino signal from the direction of NGC 4151 and assess their detectability with future neutrino observatories. We model the multi-wavelength spectral energy distributions of both blazars using a self-consistent numerical radiation code, AM$^3$. We calculate their neutrino spectra and compare them to the measured NGC 4151 neutrino spectrum and future neutrino detector sensitivities. Our models predict neutrino emission peaking at $\sim$10$^{17}$ eV for both blazars, with fluxes of ${\sim}10^{-12}~\mathrm{erg~cm^{-2}~s^{-1}}$. This indicates their contribution to the $\sim$10 TeV neutrino signal observed from the direction of NGC 4151 is minor. While detection with current facilities is challenging, both sources should be detectable by future radio-based neutrino telescopes such as IceCube-Gen2's radio array and GRAND, with 4FGL~J1210.3+3928 being the more promising candidate.