NUMERICAL SIMULATIONS OF HYDRODYNAMICAL JETS CROSSING A GALACTIC HALO INTRACLUSTER MEDIUM INTERFACE

We have performed a series of fairly high resolution two-dimensional hydrodynamical simulations of expanding axisymmetric jets using parameters expected to be reasonable for extragalactic radio sources. These model beams are initially conical and propagate first through X-ray emitting isothermal (T almost-equal-to 10(7) K) galactic halos with densities declining as a power-law of radius. These beams then cross pressure-matched interfaces into hotter but less dense media, typical of intracluster or intergalactic gases. We confirm most of the conclusions drawn from preliminary low-resolution runs (Wiita, Rosen, & Norman), particularly the slowing down in relatively shallow power-law atmospheres and the transition from conical to quasi-cylindrical beams after crossing the interface. Good agreement with analytical estimates for conical jet propagation is also found. However, these superior simulations indicate that sufficiently slow jets do become unstable after passing the interface, which was not clear from the earlier simulations. Beams whose inputs of mass and momentum are removed both before and after crossing the interface are also examined. The resulting rarefaction waves, smoothed internal pressures, and slowed forward velocities imply that minimal shock acceleration of synchrotron emitting electrons will occur once a jet is no longer being fed.