An Improved Model for the Dynamical Evolution of Dark Matter Subhaloes

TL;DR

This paper presents an enhanced analytical model for the evolution of dark matter subhaloes, incorporating key physical processes and calibration with simulations to better predict their mass, distribution, and dynamics within host halos.

Contribution

The paper introduces a revised analytical model that accounts for tidal stripping efficiency and improves predictions of subhalo properties compared to previous models.

Findings

Better match to subhalo mass function from simulations.

Predicted subhalo distribution aligns with Milky Way satellites.

Radial distribution depends mainly on accretion time.

Abstract

Using an analytical model, we study the evolution of subhalo, including its mass, angular momentum and merging time-scale. This model considers the dominant processes governing subhalo evolution, such as dynamical friction, tidal stripping and tidal heating. We find that in order to best match the evolution of angular momentum measured from N-body simulation, mass stripping by tidal force should become inefficient after subhalo has experienced a few passages of pericenter. It is also found that the often used Coulomb logarithm $\ln M/m$ has to be revised to best fit the merging time-scales from simulation. Combining the analytical model with the Extended Press-Schechter (EPS) based merger trees, we study the subhalo mass function, and their spatial distribution in a Milky-Way (MW) type halo. By tuning the tidal stripping efficiency, we can gain a better match to the subhalo mass function from simulation. The predicted distribution of subhaloes is found to agree with the distribution of MW satellites, but is more concentrated than the simulation results. The radial distribution of subhaloes depends weakly on subhaloes mass at both present day and the time of accretion, but strongly on the accretion time. Using the improved model, we measure the second moment of the subhalo occupation distribution, and it agrees well with the results of Kravtsov et al. (2004a) and Zheng et al. (2005).