Hydrodynamical Simulations of Colliding Jets

TL;DR

This paper uses 3D hydrodynamical simulations to explore how colliding extragalactic jets behave, revealing conditions for bouncing or merging interactions and explaining the observed morphology of 3C 75.

Contribution

It introduces a detailed simulation study of colliding jets, identifying conditions for different interaction outcomes and linking these to observed radio structures.

Findings

Colliding jets can bounce or merge depending on speed and impact parameter.

Merging jets can form oscillating filaments resembling a double helix.

The morphology of 3C 75 is explained by a collision of jets with different speeds.

Abstract

Radio observations suggest that 3C 75, located in the dumbbell shaped galaxy NGC 1128 at the center of Abell 400, hosts two colliding jets. Motivated by this source, we perform three-dimensional hydrodynamical simulations using a modified version of the GPU-accelerated Adaptive-MEsh-Refinement hydrodynamical parallel code ($\mathit{GAMER}$) to study colliding extragalactic jets. We find that colliding jets can be cast into two categories: 1) bouncing jets, in which case the jets bounce off each other keeping their identities, and 2) merging jets, when only one jet emerges from the collision. Under some conditions the interaction causes the jets to break up into oscillating filaments of opposite helicity, with consequences for their downstream stability. When one jet is significantly faster than the other and the impact parameter is small, the jets merge; the faster jet takes over the slower one. In the case of merging jets, the oscillations of the filaments, in projection, may show a feature which resembles a double helix, similar to the radio image of 3C 75. Thus we interpret the morphology of 3C 75 as a consequence of the collision of two jets with distinctly different speeds at a small impact parameter, with the faster jet breaking up into two oscillating filaments.