A three-dimensional model of the fluid dynamics of radio-trail sources

Abstract

Extragalactic radio sources display a wide range of complex structures. The weaker sources have twin jets emerging from the nucleus of the parent galaxy, which bend and twist as they interact with the intergalactic medium (IGM); extreme examples are the radio-trail sources, such as NGC1265 (ref. 1) and 3C129 (ref. 2). More powerful sources typically show double structures with lobes and hotspots, but even these (such as Cygtius A (R. A. Perley, personal communication)) contain curved jets. Although our theoretical understanding of sources in terms of twin plasma-jets has advanced, numerical simulations^3,4 have concentrated on axisym-metric models, whereas the investigation of radio-trail and complex sources demands three-dimensional simulations, despite the obvious computational difficulties. It is now generally accepted that radio-trail galaxies are produced by the motion of active galactic nuclei through the IGM in clusters of galaxies⁵. Models were initially proposed in which the ejected material consisted of independent blobs or plasmons^6–8, but most evidence^9,10 now supports ejection in a quasi-continuous jet^9,11. Here we adopt the jet model and study the formation of twin-tail sources by the motion of the active nucleus through intra-cluster gas, using three dimensional fluid-dynamical simulations of a supersonic jet in a cross-wind.