New class of Very High Energy gamma-ray emitter: radio-dark mini-shells surrounding AGN jets

TL;DR

This paper predicts that mini-shells surrounding AGN jets can produce detectable very high energy gamma-ray emission via inverse-Compton scattering, representing a new class of gamma-ray sources.

Contribution

It introduces a novel theoretical model for VHE gamma-ray emission from radio-dark mini-shells around AGN jets, highlighting their detectability with CTA.

Findings

Inverse-Compton emission from mini-shells can dominate at VHE energies.

Mini-shells are potential new gamma-ray sources detectable by CTA.

Radio emission from mini-shells is overshadowed by lobe emission.

Abstract

We explore non-thermal emission from a shocked interstellar medium, which is identified as an expanding shell, driven by a relativistic jet in active galactic nuclei (AGNs). In this work, we particularly focus on parsec-scale size mini-shells surrounding mini radio lobes. From radio to X-ray band, the mini radio lobe emission dominates the faint emission from the mini-shell. On the other hand, we find that inverse-Compton (IC) emission from the shell can overwhelm the associated lobe emission at very high energy (VHE; E>100 GeV) gamma-ray range, because energy densities of synchrotron photons from the lobe and/or soft photons from the AGN nucleus are large and IC scattering effectively works. The predicted IC emission from nearby mini-shells can be detected with the Cherencov Telescope Array (CTA) and they are potentially a new class of VHE gamma-ray emitters.