Radio Jet Interactions with Massive Clouds

Abstract

Three-dimensional simulations of hydrodynamic jets are computed at rather high resolution using the ZEUS-3D code. The parameters we employ are suitable for moderate-to-high-power radio jets emerging through a galactic atmosphere or halo and eventually crossing a tilted pressure-matched interface with a hotter intracluster medium. Before they cross this interface, these simulations aim the jets so that they hit massive clouds within the galactic halo, with densities 10 or more times higher than the ambient atmospheric density and hundreds to thousands times the jet density. Such clouds are set up with radii several times that of the jet and could correspond to giant molecular cloud complexes or small cannibalized galaxies. We find that while powerful jets eventually disperse the clouds, for off-center collisions, nonaxisymmetric instabilities are induced in those jets. Those instabilities grow faster for lower Mach number jets and can disrupt the jets substantially sooner than occurs for similar simulations of jets not hitting clouds. Such interactions could be related to some compact steep-spectrum source morphologies. Weak jets can be effectively halted or destroyed by reasonably massive clouds, and this type of interaction may have relevance for the paucity of extended radio jets in spiral galaxies. Slow, dense jets may be bent yet remain stable for fairly extended times, and such interactions can be responsible for some of the wide-angle tail and most of the "dogleg" radio source morphologies.