Tidal interaction of galaxies

In this paper we investigate the effect of weak tidal interactions among galaxies in clusters. We obtain the Fokker-Planck coefficients for this process by making use of the impulse approximation. We assume that the outer regions of a galaxy are well described by isotropically distributed stellar orbits with small angular momenta. In this case the stellar distribution function is a function of energy and time only. We are able to solve the resulting Fokker-Planck equation for power-law potentials, and find that there are no globally self-consistent solutions of this type. Our calculation indicates that stars are preferentially stripped from the outer regions rather than forming a relaxed extended envelope. We conclude that the effect of the fluctuating term in the tidal force is qualitatively similar to that of the usual secular term