Hydrodynamic Models of Radio Galaxy Morphology: Winged and X-shaped Sources

TL;DR

This study uses 3D hydrodynamic simulations to investigate how hot atmosphere interactions and jet dynamics lead to winged and X-shaped radio galaxy structures, highlighting the role of backflow deflection and environmental factors.

Contribution

The paper introduces detailed hydrodynamic models explaining the formation of winged and X-shaped radio galaxy morphologies, emphasizing the influence of hot atmosphere gradients and jet behavior.

Findings

Wings form through backflow deflection and buoyant expansion.

Prominent wings occur with decaying jets in elliptical atmospheres.

Atmosphere-jet interactions significantly influence galaxy morphology.

Abstract

We present three-dimensional hydrodynamic models of radio galaxies interacting with initially relaxed hot atmospheres and explore the significant off-axis radio lobe structures which result under certain conditions. With a focus on the "winged" and "X-shaped" radio galaxy population, we confirm the importance of observed trends such as the connection of wing formation with jets co-aligned with the major axis of the surrounding atmosphere. These wings are formed substantially by the deflection of lobe plasma flowing back from the hot spots (backflow) and develop in two stages: supersonic expansion of an overpressured cocoon at early times followed by buoyant expansion at later times. We explore a limited parameter space of jet and atmosphere properties and find that the most prominent wings are produced when a decaying jet is injected into a small, dense, highly elliptical atmosphere. On the basis of this search, we argue that the deflection of backflow by gradients in the hot atmosphere is a strong candidate for forming observed wings but must work in tandem with some other mechanism for forming the initial wing channels. Our models indicate that lobe interaction with the hot atmosphere may play a dominant role in shaping the morphology of radio galaxies.