Renegade Subhaloes in the Local Group

TL;DR

This study uses a constrained simulation of the Local Group to investigate the existence and properties of 'renegade' subhaloes that switch hosts, finding they are rare and difficult to distinguish observationally.

Contribution

It provides the first detailed analysis of renegade subhaloes in a Local Group simulation, highlighting their rarity and complex behavior without requiring mergers.

Findings

Renegade subhaloes are rare and often pass by hosts before being captured.

They do not necessarily originate from deep within the host potential wells.

Differences in velocity, distribution, shape, and spin can help identify them.

Abstract

Using a dark matter only Constrained Local UniversE Simulation (CLUES) we examine the existence of subhaloes that change their affiliation from one of the two prominent hosts in the Local Group (i.e. the Milky Way and the Andromeda galaxy) to the other, and call these objects "renegade subhaloes". In light of recent claims that the two Magellanic Clouds (MCs) may have originated from another region (or even the outskirts) of the Local Group or that they have been spawned by a major merger in the past of the Andromeda galaxy, we investigate the nature of such events. However, we cannot confirm that renegade subhaloes enter as deep into the potential well of their present host nor that they share the most simplest properties with the MCs, namely mass and relative velocity. Our simulation rather suggests that these renegade subhaloes appear to be flying past one host before being pulled into the other. A merger is not required to trigger such an event, it is rather the distinct environment of our simulated Local Group facilitating such behavior. Since just a small fraction of the full z=0 subhalo population are renegades, our study indicates that it will be intrinsically difficult to distinguish them despite clear differences in their velocity, radial distribution, shape and spin parameter distributions.