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 h otter, 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 al so gave rise to preliminary estimates for the continued expansion and fading of radio sources whose source of plasma was cut off. We now pre sent runs which go on for substantially longer times, corresponding to over 10(8) yr, with jets propagating several hundred times their orig inal radii, or to approximately 400 kpc. More realistic ISM/ICM interf aces have also been treated, as have boundary conditions spanning the physically plausible situations. Jets with Mach numbers around 3 event ually find their bow-shocks weakening and the jet's progress essential ly stalls. Instabilities leading to the separation of the outer part o f the jet from the source of plasma in the nucleus are found even in t hese axisymmetric situations. We find this separation can be followed by the production of new Mach disks and concomitant radio hot spots, w ell behind the original, and now rapidly fading, working surface. Exam ples of such sources may be 3C 200, 3C 219, 3C 249.1, and the radio qu asar 1732+655. These results also may have implications for the rarity and extent of giant radio galaxies.