Radio jet interactions with massive clouds

Three-dimensional simulations of hydrodynamic jets are computed at rather h igh resolution using the ZEUS-3D code. The parameters we employ are suitabl e for moderate-to-high-power radio jets emerging through a galactic atmosph ere or halo and eventually crossing a tilted pressure-matched interface wit h a hotter intracluster medium. Before they cross this interface, these sim ulations aim the jets so that they hit massive clouds within the galactic h alo, with densities 10 or more times higher than the ambient atmospheric de nsity 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 m olecular cloud complexes or small cannibalized galaxies. We find that while powerful jets eventually disperse the clouds, for off-center collisions, n onaxisymmetric instabilities are induced in those jets. Those instabilities grow faster for lower Mach number jets and can disrupt the jets substantia lly sooner than occurs for similar simulations of jets not hitting clouds. Such interactions could be related to some compact steep-spectrum source mo rphologies. Weak jets can be effectively halted or destroyed by reasonably massive clouds, and this type of interaction may have relevance for the pau city of extended radio jets in spiral galaxies. Slow, dense jets may be ben t 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.