Modelling the dynamical friction timescale of sinking satellite
Abstract
When a satellite galaxy falls into a massive dark matter halo, it suffers the dynamical friction force which drag it into the halo center and finally it merger with the central galaxy. The time interval between entry and merger is called as the dynamical friction timescale (Tdf). Many studies have been dedicated to derive Tdf using analytical models or N-body simulations. These studies have obtained qualitative agreements on how Tdf depends on the orbit parameters, and mass ratio between satellite and host halo. However, there are still disagreements on the accurate form of Tdf . In this paper, we present a semi-analytical model to predict Tdf and we focus on interpreting the discrepancies among different studies. We find that the treatment of mass loss from satellite by tidal stripping dominates the behavior of Tdf . We also identify other model parameters which affect the predicted Tdf.