Structures produced by the collision of extragalactic jets with dense clouds

We investigate how several parameters can affect the results of a collision between an extragalactic jet and a dense, intergalactic cloud, through a s eries of hydrodynamic simulations. Such collisions are often suggested to e xplain the distorted structures of some radio jets, However, theoretical st udies of this mechanism are in conflict over whether it can actually reprod uce the observations. The parameters are the Mach number, and the relative densities of the jet a nd the cloud to the ambient medium. Using a simple prescription, we have pr oduced synthetic radio images for comparison with observations. These show that a variety of structures may be produced from simple jet-cloud collisio ns. We illustrate this with a few examples, and examine the details in one case. In most cases we do not see a clear, sustained deflection. Lighter je ts are completely disrupted. The most powerful jets produce a hotspot at th e impact which outshines any jet emission, and erode the cloud too quickly to develop a deflected arm. It appears that moderate Mach numbers and densi ty contrasts are needed to produce bends in the radio structure. This expla ins the apparent conflict between theoretical studies, as conclusions were based on different values of these parameters. Shocks are produced in the a mbient medium that might plausibly reproduce the observed alignment of the extended emission-line regions with the radio axis.