An analytical model for the accretion of dark matter subhalos

TL;DR

This paper presents a simple analytical model for the distribution and accretion history of dark matter subhalos, validated against simulations, with implications for galaxy-halo evolution.

Contribution

It introduces a novel, straightforward analytical model combining existing halo assembly theories to predict subhalo properties and their evolution.

Findings

Model predictions match high-resolution simulation results.

The model accurately predicts subhalo mass functions and accretion times.

Implications for galaxy and dark matter halo evolution are discussed.

Abstract

An analytical model is developed for the mass function of cold dark matter subhalos at the time of accretion and for the distribution of their accretion times. Our model is based on the model of Zhao et al. (2009) for the median assembly histories of dark matter halos, combined with a simple log-normal distribution to describe the scatter in the main-branch mass at a given time for halos of the same final mass. Our model is simple, and can be used to predict the un-evolved subhalo mass function, the mass function of subhalos accreted at a given time, the accretion-time distribution of subhalos of a given initial mass, and the frequency of major mergers as a function of time. We test our model using high-resolution cosmological $N$-body simulations, and find that our model predictions match the simulation results remarkably well. Finally, we discuss the implications of our model for the evolution of subhalos in their hosts and for the construction of a self-consistent model to link galaxies and dark matter halos at different cosmic times.