Fossil shell emission in dying radio loud AGNs

TL;DR

This paper models the evolution of shell emission in dying radio loud AGNs, revealing that fossil shells can outshine radio lobes post-jet activity and may be detectable in gamma rays by CTA.

Contribution

It introduces a new model describing shell emission evolution after jet activity ceases, highlighting fossil shells as potential targets for SKA and CTA observations.

Findings

Shell emission dominates radio lobes after jet stops.

Fossil shells are bright in TeV gamma-ray band.

Potential detectability of fossil shells with CTA.

Abstract

We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolutions of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in radio band while it is bright in TeV gamma-ray band and it can be detectable by CTA.