The Preferential Tidal Stripping of Dark Matter versus Stars in Galaxies

TL;DR

This study uses high-resolution simulations to show that dark matter is more extensively stripped than stars in galaxies due to their different initial distributions, with implications for modeling galaxy evolution.

Contribution

It provides new quantitative relations for dark matter and stellar stripping, highlighting the stellar-to-halo size ratio as a key parameter, applicable across various galaxy and cluster masses.

Findings

Dark matter is stripped more than stars in galaxies.

Stellar-to-halo size ratio controls stripping efficiency.

Stripping relations are broadly applicable regardless of galaxy or cluster mass.

Abstract

Using high resolution hydrodynamical cosmological simulations, we conduct a comprehensive study of how tidal stripping removes dark matter and stars from galaxies. We find that dark matter is always stripped far more significantly than the stars -- galaxies that lose $\sim$80$\%$ of their dark matter, typically lose only 10$\%$ of their stars. This is because the dark matter halo is initially much more extended than the stars. As such, we find the stellar-to-halo size-ratio (measured using r$_{\rm{eff}}$/r$_{\rm{vir}}$) is a key parameter controlling the relative amounts of dark matter and stellar stripping. We use simple fitting formulae to measure the relation between the fraction of bound dark matter and fraction of bound stars. We measure a negligible dependence on cluster mass or galaxy mass. Therefore these formulae have general applicability in cosmological simulations, and are ideal to improve stellar stripping recipes in semi-analytical models, and/or to estimate the impact that tidal stripping would have on galaxies when only their halo mass evolution is known.