Isotropic Steady States in Galactic Dynamics

The present paper completes our earlier results on nonlinear stability of stationary solutions of the Vlasov--Poisson system in the stellar dynamics case. By minimizing the energy under a mass-Casimir constraint we construct a large class of isotropic, spherically symmetric steady states and prove their nonlinear stability against {general}, i. e., not necessarily symmetric perturbations. The class is optimal in a certain sense, in particular, it includes all polytropes of finite mass with decreasing dependence on the particle energy.