The grouping, merging and survival of subhaloes in the simulated Local Group

TL;DR

This study uses a realistic Local Group simulation to analyze subhalo evolution, focusing on tidal stripping, interactions, and mergers, revealing their timing and impact on dwarf galaxy formation.

Contribution

It provides new insights into the timing and effects of subhalo mergers, interactions, and tidal stripping within a Local Group-like environment.

Findings

Subhaloes undergo tidal stripping at infall, affecting their mass function.

Most mergers occur more than 7 Gyr ago outside host haloes.

Recent large group infall could explain satellite distribution peculiarities.

Abstract

We use a simulation performed within the Constrained Local UniversE Simulation (CLUES) project to study a realistic Local Group-like object. We employ this group as a numerical laboratory for studying the evolution of the population of its subhaloes from the point of view of the effects it may have on the origin of different types of dwarf galaxies. We focus on the processes of tidal stripping of the satellites, their interaction, merging and grouping before infall. The tidal stripping manifests itself in the transition between the phase of mass accretion and mass loss seen in most subhaloes, which occurs at the moment of infall on to the host halo, and the change of the shape of their mass function with redshift. Although the satellites often form groups, they are loosely bound within them and do not interact with each other. The infall of a large group could however explain the observed peculiar distribution of the Local Group satellites, but only if it occurred recently. Mergers between prospective subhaloes are significant only during an early stage of evolution, i.e. more than 7 Gyr ago, when they are still outside the host haloes. Such events could thus contribute to the formation of more distant early type Milky Way companions. Once the subhaloes enter the host halo the mergers become very rare.