Interactions of a Light Hypersonic Jet with a Non-Uniform Interstellar Medium

TL;DR

This paper uses 3D simulations to study how a light hypersonic jet interacts with an inhomogeneous interstellar medium, revealing four evolutionary phases and proposing a model for observed jet structures.

Contribution

It introduces a detailed simulation-based analysis of jet-ISM interactions, identifying four generic phases and modeling morphology and motions in a specific compact symmetric object.

Findings

Identified four phases of jet evolution in an inhomogeneous medium.

Proposed a model explaining morphology and proper motions in 4C31.04.

Demonstrated how jets break out and become collimated in complex environments.

Abstract

We present three dimensional simulations of the interaction of a light hypersonic jet with an inhomogeneous thermal and turbulently supported disk in an elliptical galaxy. We model the jet as a light, supersonic non-relativistic flow with parameters selected to be consistent with a relativistic jet with kinetic power just above the FR1/FR2 break. We identify four generic phases in the evolution of such a jet with the inhomogeneous interstellar medium: 1) an initial ``flood and channel'' phase, where progress is characterized by high pressure gas finding changing weak points in the ISM, flowing through channels that form and re-form over time, 2) a spherical, energy-driven bubble phase, were the bubble is larger than the disk scale, but the jet remains fully disrupted close to the nucleus, 3) a rapid, jet break--out phase the where jet breaks free of the last dense clouds, becomes collimated and pierces the spherical bubble, and 4) a classical phase, the jet propagates in a momentum-dominated fashion leading to the classical jet + cocoon + bow-shock structure. Mass transport in the simulations is investigated, and we propose a model for the morphology and component proper motions in the well-studied Compact Symmetric Object 4C31.04.