Simple Distribution Functions for Stellar Disks

Distribution functions (DFs) for dynamically warm thin stellar disks residingin arbitrary axisymmetric potentials are presented which approximatelyreproduce pre-described surface-density and velocity-dispersion profiles. Thefunctional form of the DFs is obtained by `warming-up' a model made entirely ofcircular orbits. This can be done in various ways giving different functionalforms for the DF. In the best case, the DF reproduces the pre-describedprofiles to within a few per cent for a typical case reminiscent to the oldstellar disk in the Milky Way. This match may be improved to about one per centor better by a simple iterative method. An algorithm is given to drawphase-space points randomly from the DFs for the purpose of, e.g., N-bodysimulations. All the relevant computer programs are available from the author.Comment: accepted for publication in AJ, 10 pages, 5 figures (coloured only here, not in AJ), uses aas2pp4.st