Tidal Mass Loss from Collisionless Systems

Abstract

We examine the problem tidally-induced mass loss from collisionless systems such as dark matter haloes. We develop a model for tidal mass loss, based upon the phase space distribution of particles, which accounts for how both tidal and Coriolis torques perturb the angular momentum of each particle in the system. This allows us to study how both the density profile and velocity anisotropy affect the degree of mass loss--we present basic results from such a study. Our model predicts that mass loss is a continuous process even in a static tidal field, a consequence of the fact that mass loss weakens the potential of the system making it easier for further mass loss to occur. We compare the predictions of our model with N-body simulations of idealized systems in order to check its validity. We find reasonable agreement with the N-body simulations except for in the case of very strong tidal fields, where our results suggest that a higher-order perturbation analysis may be required. The continuous tidally-induced mass loss predicted by our model can lead to substantial reduction in satellite mass in cases where the traditional treatment predicts no mass loss. As such, our results may have important consequences for the orbits and survival of low mass satellites in dark matter haloes.