Superdisks in Radio Galaxies: Jet-Wind Interactions

TL;DR

This paper proposes a new mechanism involving jet-wind interactions to explain the sharp-edged emission gaps in radio galaxies, especially where traditional models struggle, by considering the confinement of thermal winds by radio lobes.

Contribution

It introduces a novel dynamical interaction model between AGN thermal winds and radio lobe plasma to explain large radio gaps, addressing limitations of previous explanations.

Findings

Analytical scheme supports side-ways wind confinement by radio lobes.

Explains formation of large, sharp-edged radio gaps in high-redshift galaxies.

Suggests hot wind escape routes orthogonal to radio jets.

Abstract

Taking a clue from their sharp-edged (strip-like) morphology observed in several cases, a new mechanism is proposed for the formation of the emission gaps seen between the radio lobes of many powerful extragalactic double radio sources. Canonical understanding of the radio gaps invokes either blocking of the back-flowing lobe plasma by the denser interstellar medium (ISM) of the host galaxy, or "squeezing" of the radio bridge in the middle through buoyancy force exerted by either the ISM or the surrounding intra-cluster medium (ICM). These pictures encounter difficulties in explaining situations where the sharp-edged radio gaps associated with non-cluster radio galaxies have widths running into several tens (even hundreds) of kiloparsecs. More particularly, the required dense high-pressure ISM/ICM is likely to be lacking at least in the case of high-redshift radio galaxies. We propose here that radio emission gaps in at least such cases could arise from a dynamical interaction between the powerful thermal wind outflowing from the active galactic nucleus and the back-flowing synchrotron plasma in the two radio lobes, which occurs once the rapidly advancing jets have crossed out of the wind zone into the intergalactic medium. A simple analytical scheme is presented to explore the plausibility of the side-ways confinement of the thermal wind by the radio lobe pair, which would "freeze" pancake shaped conduits in the space, along which the hot, metal enriched wind from the AGN can escape (roughly orthogonal to the radio axis). Some other possible consequences of this scenario are pointed out.