Evolution of non-thermal emission from shell associated with AGN jets

TL;DR

This paper models the evolution of non-thermal emission from shocked shells driven by AGN jets, predicting observable gamma-ray signatures that depend on source size and luminosity.

Contribution

It provides a detailed analysis of broadband emission spectra considering cooling effects, and predicts detectable TeV gamma-ray emissions from AGN jet-driven shells.

Findings

IC emission dominates in compact sources (<10 kpc).

Shell emissions surpass lobe emissions at IR and optical bands for >10 kpc sources.

TeV gamma-rays from shells are detectable with current Cherenkov telescopes.

Abstract

We explore the evolution of the emissions by accelerated electrons in shocked shells driven by jets in active galactic nuclei (AGNs). Focusing on powerful sources which host luminous quasars, we evaluated the broadband emission spectra by properly taking into account adiabatic and radiative cooling effects on the electron distribution. The synchrotron radiation and inverse Compton (IC) scattering of various photons that are mainly produced in the accretion disc and dusty torus are considered as radiation processes. We show that the resultant radiation is dominated by the IC emission for compact sources (< 10kpc), whereas the synchrotron radiation is more important for larger sources. We also compare the shell emissions with those expected from the lobe under the assumption that a fractions of the energy deposited in the shell and lobe carried by the non-thermal electrons are $\epsilon_e \sim 0.01$ and $\epsilon_{e, lobe} \sim 1$, respectively. Then, we find that the shell emissions are brighter than the lobe ones at infra-red and optical bands when the source size is > 10kpc, and the IC emissions from the shell at > 10 GeV can be observed with the absence of contamination from the lobe irrespective of the source size. In particular, it is predicted that, for most powerful nearby sources ($L_j \sim 10^{47} ergs s^{-1}$), TeV gamma-rays produced via the IC emissions can be detected by the modern Cherenkov telescopes such as MAGIC, HESS and VERITAS.