Neutrino, $\gamma$-ray and cosmic ray fluxes from the core of the closest radio galaxies

TL;DR

This paper models the broadband emission from the closest radio galaxies using a lepto-hadronic approach, predicting neutrino and cosmic ray fluxes, and compares these with observations to explore their potential as high-energy particle sources.

Contribution

It introduces a combined lepto-hadronic model for radio galaxy emissions, linking gamma-ray, neutrino, and cosmic ray production with observational data.

Findings

TeV gamma-ray spectra may have a hadronic origin.

Expected neutrino fluxes are insufficient to explain IceCube observations.

Ultra-high-energy cosmic ray connection to Centaurus A requires heavy nuclei.

Abstract

The closest radio galaxies; Centaurus A, M87 and NGC 1275, have been detected from radio wavelengths to TeV $\gamma$-rays, and also studied as high-energy neutrino and ultra-high-energy cosmic ray potential emitters. Their spectral energy distributions show a double-peak feature, which is explained by synchrotron self-Compton model. However, TeV $\gamma$-ray measured spectra could suggest that very-high-energy $\gamma$-rays might have a hadronic origin. We introduce a lepto-hadronic model to describe the broadband spectral energy distribution; from radio to sub GeV photons as synchrotron self-Compton emission and TeV $\gamma$-ray photons as neutral pion decay resulting from p$\gamma$ interactions occurring close to the core. These photo-hadronic interactions take place when Fermi-accelerated protons interact with the seed photons around synchrotron self-Compton peaks. Obtaining a good description of the TeV $\gamma$-ray fluxes, firstly, we compute neutrino fluxes and events expected in IceCube detector and secondly, we estimate ultra-high-energy cosmic ray fluxes and event rate expected in Telescope Array, Pierre Auger and HiRes observatories. Within this scenario we show that the expected high-energy neutrinos cannot explain the astrophysical flux observed by IceCube, and the connection with ultra-high-energy cosmic rays observed by Auger experiment around Centaurus A, might be possible only considering a heavy nuclei composition in the observed events.