LONG-TERM HYDRODYNAMICAL SIMULATIONS OF EXTRAGALACTIC RADIO JETS

Moderately high-resolution two-dimensional hydrodynamical simulations of initially conical low-density jets have been performed. These jets, with parameters believed to be suitable for powerful radio galaxies, emerge from the atmospheres of active galaxies and then cross into a hotter, but less dense, intracluster medium, whereupon they accelerate and collimate. Earlier simulations led to results on instabilities in slow jets and the rate of jet advance within galactic halos that were in good agreement with analytical approximations. Those simulations also gave rise to preliminary estimates for the continued expansion and fading of radio sources whose source of plasma was cut off. We now present runs which go on for substantially longer times, corresponding to over 10(8) yr, with jets propagating several hundred times their original radii, or to approximately 400 kpc. More realistic ISM/ICM interfaces have also been treated, as have boundary conditions spanning the physically plausible situations. Jets with Mach numbers around 3 eventually find their bow-shocks weakening and the jet's progress essentially stalls. Instabilities leading to the separation of the outer part of the jet from the source of plasma in the nucleus are found even in these axisymmetric situations. We find this separation can be followed by the production of new Mach disks and concomitant radio hot spots, well behind the original, and now rapidly fading, working surface. Examples of such sources may be 3C 200, 3C 219, 3C 249.1, and the radio quasar 1732+655. These results also may have implications for the rarity and extent of giant radio galaxies.