Observational dynamics of low-mass stellar systems

TL;DR

This paper reviews the recent discoveries and internal dynamics of low-mass stellar systems, focusing on ultra-compact dwarf galaxies and diffuse globular clusters, to understand their origins and classification.

Contribution

It provides a comprehensive review of the properties and dynamical studies of UCDs and diffuse GCs, highlighting their significance at the galaxy-star cluster interface.

Findings

Recent observational data on UCDs' internal dynamics

Dynamical considerations for diffuse GCs

Insights into the origin and evolution of low-mass stellar systems

Abstract

The last fifteen years have seen the discovery of new types of low-mass stellar systems that bridge the gap between the once well-separated regimes of galaxies and of star clusters. Whether such objects are considered galaxies depends also on the definition of the term "galaxy", and several possible criteria are based on their internal dynamics (e.g. the common concept that galaxies contain dark matter). Moreover, studying the internal dynamics of low-mass stellar systems may also help understand their origin and evolutionary history. The focus of this paper is on two classes of stellar systems at the interface between star clusters and dwarf galaxies: ultra-compact dwarf galaxies (UCDs) and diffuse Galactic globular clusters (GCs). A review of our current knowledge on the properties of UCDs is provided and dynamical considerations applying to diffuse GCs are introduced. In the following, recent observational results on the internal dynamics of individual UCDs and diffuse Galactic globular clusters are presented.