Comparing the observable properties of dwarf galaxies on and off the Andromeda plane

TL;DR

This study compares the properties of dwarf galaxies on and off the Andromeda plane, finding no significant differences in their evolution, challenging the idea that on-plane dwarfs have distinct formation histories.

Contribution

It provides the first comprehensive comparison of on- and off-plane dwarf galaxies in Andromeda using new kinematic data and existing observations.

Findings

On- and off-plane dwarfs are indistinguishable in properties.

No evidence of different evolutionary histories between the two groups.

Results challenge the hypothesis of distinct formation mechanisms for on-plane dwarfs.

Abstract

The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the LCDM paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) to their off-plane neighbours. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for 2 on-plane M31 dSphs (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.