Equilibria of flat and round galactic disks

Abstract

A general method is presented for constructing distribution functions for flat systems whose surface density and Toomre's Q number profile is given. The purpose of these functions is to provide plausible galactic models and assess their critical stability with respect to global non axi-symmetric modes. The derivation may be carried out for an azimuthal velocity distribution (or a given specific energy distribution) which may either be observed or chosen to match a specified temperature profile. Distribution functions describing stable models with realistic velocity distributions for power law disks, the Isochrone and the Kuzmin disks are provided. Specially simple inversion formulae are also given for finding distribution functions for flat systems whose surface densities are known.