SPHERICAL GALAXIAN DISTRIBUTION-FUNCTIONS WITH ADJUSTABLE ANISOTROPY

Building on a recent idea by Louis, a simple numerical procedure is developed which recovers, for a given spherical potential density pair, the phase-space distribution function. This corresponds, for the first time, to a class of models for which we are able to assign a priori any asymptotic value of velocity anisotropy, for systems of both infinite and finite extent. A second free parameter in these models is an 'anisotropy radius', which determines the extent to which the anisotropy is localized in space. The method, which is illustrated here for the simple case of the Plummer potential density pair, should prove particularly useful in furthering our understanding of the role played by anisotropies in generating observed line profiles and of their role in the complex subject of dynamical instabilities.