Structures produced by the collision of extragalactic jets with dense clouds

S W Higgins, T J O'Brien, J S Dunlop

Research output: Contribution to journalArticlepeer-review


We investigate how several parameters can affect the results of a collision between an extragalactic jet and a dense, intergalactic cloud, through a series of hydrodynamic simulations. Such collisions are often suggested to explain the distorted structures of some radio jets, However, theoretical studies of this mechanism are in conflict over whether it can actually reproduce the observations.

The parameters are the Mach number, and the relative densities of the jet and the cloud to the ambient medium. Using a simple prescription, we have produced synthetic radio images for comparison with observations. These show that a variety of structures may be produced from simple jet-cloud collisions. 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 jets are completely disrupted. The most powerful jets produce a hotspot at the impact which outshines any jet emission, and erode the cloud too quickly to develop a deflected arm. It appears that moderate Mach numbers and density contrasts are needed to produce bends in the radio structure. This explains the apparent conflict between theoretical studies, as conclusions were based on different values of these parameters. Shocks are produced in the ambient medium that might plausibly reproduce the observed alignment of the extended emission-line regions with the radio axis.

Original languageEnglish
Pages (from-to)273-286
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 21 Oct 1999


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