Stability of Satellite Planes in M31 II: Effects of the Dark Subhalo Population

TL;DR

This study investigates how dark matter subhalos and halo shape influence the stability of satellite galaxy planes in M31, revealing that subhalo interactions and misalignments reduce their longevity.

Contribution

It provides new insights into the effects of dark matter subhalo populations and halo shape on the stability and lifetime of satellite galaxy planes.

Findings

More dark subhalos hasten plane deterioration.

Misalignments with halo axes reduce plane lifetime to under 3 Gyr.

High subhalo mass fractions (>40%) lead to unstable satellite planes.

Abstract

The planar arrangement of nearly half the satellite galaxies of M31 has been a source of mystery and speculation since it was discovered. With a growing number of other host galaxies showing these satellite galaxy planes, their stability and longevity have become central to the debate on whether the presence of satellite planes are a natural consequence of prevailing cosmological models, or represent a challenge. Given the dependence of their stability on host halo shape, we look into how a galaxy plane's dark matter environment influences its longevity. An increased number of dark matter subhalos results in increased interactions that hasten the deterioration of an already-formed plane of satellite galaxies in spherical dark halos. The role of total dark matter mass fraction held in subhalos in dispersing a plane of galaxies present non trivial effects on plane longevity as well. But any misalignments of plane inclines to major axes of flattened dark matter halos lead to their lifetimes being reduced to < 3 Gyrs. Distributing > 40% of total dark mass in subhalos in the overall dark matter distribution results in a plane of satellite galaxies that is prone to change through the 5 Gyr integration time period.