Bi-symmetric instabilities of the Kuz'min/Toomre disc.

This paper reports a numerical study of the effect of random motion on the unstable bar-forming modes of one type of stellar disc mass model. From measurements of the growth rates of the few most unstable bi-symmetric modes the authors evaluate the stabilizing influence of both random motion and halo mass. They find that the growth rate of bars is a simple function of these two variables. Their results suggest that the large degree of random motion recently observed near the centres of galactic discs substantially reduces the halo mass needed to understand their stability.