Modelling the dynamical friction timescale of sinking satellite

TL;DR

This paper introduces a semi-analytical model for the dynamical friction timescale of sinking satellites, emphasizing the role of tidal stripping and other parameters in predicting merger times.

Contribution

The study provides a new semi-analytical approach to predict T_df and clarifies the impact of satellite mass loss and model parameters on its accuracy.

Findings

Mass loss from satellites via tidal stripping significantly influences T_df.

Discrepancies among models are mainly due to different treatments of tidal stripping.

Other model parameters also affect the predicted dynamical friction timescale.

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 (T_df). Many studies have been dedicated to derive T_df using analytical models or N-body simulations. These studies have obtained qualitative agreements on how T_df depends on the orbit parameters, and mass ratio between satellite and host halo. However, there are still disagreements on the accurate form of T_df . In this paper, we present a semi-analytical model to predict T_df 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 T_df . We also identify other model parameters which affect the predicted T_df.