Simple Distribution Functions for Stellar Disks

Distribution functions (DFs) for dynamically warm thin stellar disks residing in arbitrary axisymmetric potentials are presented which approximately reproduce pre-described surface-density and velocity-dispersion profiles. The functional form of the DFs is obtained by ‘warming-up’ a model made entirely of circular orbits. This can be done in various ways giving different functional forms for the DF. In the best case, the DF reproduces the pre-described profiles to within a few per cent for a typical case reminiscent to the old stellar disk in the Milky Way. This match may be improved to about one per cent or better by a simple iterative method. An algorithm is given to draw phase-space points randomly from the DFs for the purpose of, e.g., N -body simulations. All the relevant computer programs are available from the author. Subject headings: celestial mechanics, stellar dynamics – Galaxy: kinematics and dynamics – galaxies: kinematics and dynamics – galaxies: spiral – methods: analytical 1e-mail: [email protected]