Chemo-dynamical substructure in the M31 inner halo globular clusters: Further evidence for a recent accretion event

TL;DR

This study identifies a distinct, metal-poor, co-rotating substructure of globular clusters in M31's inner halo, providing evidence for a recent, significant accretion event that may be linked to outer halo structures.

Contribution

It reveals a new substructure in M31's inner halo globular clusters and links it to a recent accretion event, advancing understanding of galaxy assembly.

Findings

Identification of the Dulais Structure as a co-rotating globular cluster group

Alignment of the structure's orbital axis with a known outer halo accretion event

Evidence suggesting a recent, substantial progenitor accretion (~10^11 Msun)

Abstract

Based upon a metallicity selection, we identify a significant sub-population of the inner halo globular clusters in the Andromeda Galaxy which we name the Dulais Structure. It is distinguished as a co-rotating group of 10-20 globular clusters which appear to be kinematically distinct from, and on average more metal-poor than, the majority of the inner halo population. Intriguingly, the orbital axis of this Dulais Structure is closely aligned with that of the younger accretion event recently identified using a sub-population of globular clusters in the outer halo of Andromeda, and this is strongly suggestive of a causal relationship between the two. If this connection is confirmed, a natural explanation for the kinematics of the globular clusters in the Dulais Structure is that they trace the accretion of a substantial progenitor (~10^11 Msun) into the halo of Andromeda during the last few billion years, that may have occurred as part of a larger group infall.