NUMERICAL-CALCULATION OF LINEAR-MODES IN STELLAR DISKS

We present a method for solving the two-dimensional linearized collisi onless Boltzmann equation using Fourier expansion along the orbits. It resembles very much solutions present in the literature, but it diffe rs by the fact that everything is performed in coordinate space instea d of using action-angle variables. We show that this approach, though less elegant, is both feasible and straightforward. This approach is t hen incorporated in a matrix method in order to calculate self-consist ent modes, using a set of potential-density pairs which is obtained nu merically. We investigated the stability of some unperturbed disks hav ing an almost hat rotation curve, an exponential disk and a non-zero v elocity dispersion. The influence of the velocity dispersion, halo mas s and anisotropy on the stability is further discussed.