TeV gamma-rays from UHECR interactions in AGN cores: Lessons from Centaurus A

TL;DR

This paper explores the possibility that TeV gamma-rays from AGN cores, specifically Centaurus A, are secondary products of ultra-high-energy cosmic ray interactions, providing an alternative to leptonic jet models.

Contribution

It introduces a model where VHE gamma-rays originate from UHECR interactions in AGN cores, explaining observations despite high IR and UV backgrounds.

Findings

TeV gamma-rays can escape AGN cores despite dense IR and UV backgrounds.

The model can reconcile multi-wavelength observations of Centaurus A.

Secondary gamma-ray production from UHECRs is a viable alternative to leptonic models.

Abstract

TeV gamma-rays have been observed from blazars as well as from radio galaxies like M87 and Cen A. In leptonic models, gamma-rays above the pair production threshold can escape from the ultra-relativistic jet, since large Lorentz factors reduce the background photon densities compared to those required for isotropic emission. Here we discuss an alternative scenario, where VHE photons are generated as secondaries from UHECR interaction in the AGN core. We show that TeV gamma-rays can escape from the core despite large IR and UV backgrounds. For the special case of Cen A, we study if the various existing observations from the far infra-red to the UHE range can be reconciled within this picture.