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J.E. Cazes, J.E. Tohline (LSU)
We have long believed that there exist compressible analogs to the equilibrium sequences of incompressible self-gravitating Riemann ellipsoids , but in the past it has only been possible to create compressible nonaxisymmetric models with no internal motions. We have two examples of a stable nonaxisymmetric compressible, self-gravitating fluid configurations with nontrivial internal supersonic motions.
Both models have been constructed via dynamical simulations that have started from initially axisymmetric, rapidly rotating (T/|W|=0.3) polytropes that were dynamically unstable toward the development of a bar-like or two-armed spiral structure. The two initial models differed mainly in their angular momentum distributions: One had an n'=0 angular momentum distribution, the other had uniform vortensity. In each case, the nonlinear development of the instability resulted in an ellipsoidal-like configuration that is spinning with a well-defined pattern speed and that has strongly differential internal motions. These final, steady-state configurations are dynamically stable. These results are relevant to self-consistent models of galaxies, rapidly spinning neutron stars, and the structure and evolution of protostellar gas clouds.