Accretion in action: phase space coherence of stellar debris and globular clusters in Andromeda's South-West Cloud

TL;DR

This study provides kinematic evidence that globular clusters and stellar debris in Andromeda's South-West Cloud are linked, supporting the idea that galaxy halos grow through accretion of smaller systems including clusters.

Contribution

It offers new kinematic measurements confirming the association of globular clusters with stellar substructures in Andromeda, illustrating galaxy growth via accretion.

Findings

Kinematic properties of the South-West Cloud match those of globular cluster PA-8.

Globular clusters are associated with stellar debris in galaxy halos.

Supports galaxy formation models involving accretion of smaller systems.

Abstract

A central tenet of the current cosmological paradigm is that galaxies grow over time through the accretion of smaller systems. Here, we present new kinematic measurements near the centre of one of the densest pronounced substructures, the South-West Cloud, in the outer halo of our nearest giant neighbour, the Andromeda galaxy. These observations reveal that the kinematic properties of this region of the South-West Cloud are consistent with those of PA-8, a globular cluster previously shown to be co-spatial with the stellar substructure. In this sense the situation is reminiscent of the handful of globular clusters that sit near the heart of the Sagittarius dwarf galaxy, a system that is currently being accreted into the Milky Way, confirming that accretion deposits not only stars but also globular clusters into the halos of large galaxies.