Stellar population properties of the most massive globular clusters and ultra-compact dwarf galaxies of the Fornax cluster

TL;DR

This study investigates the properties of ultra-compact dwarf galaxies and massive globular clusters in the Fornax cluster, revealing their mass functions, origins, and stellar populations through extensive observations and simulations.

Contribution

It provides new constraints on the mass function, origin, and stellar content of UCDs in the Fornax cluster, including evidence for their formation from nuclear star clusters.

Findings

Mass function of UCDs is consistent with Gaussian GCs.

Approximately 40% of massive UCDs may originate from nuclear star clusters.

Some UCDs show young ages and He-enriched populations.

Abstract

Most ultra-compact dwarf galaxies (UCDs) and very massive globular clusters reside in nearby galaxy clusters or around nearby giant galaxies. Due to their distance (>Mpc) and compactness (r_eff<100pc) they are barely resolved, and thus it is difficult to obtain their internal properties. Here I present our most recent attempts to constrain the mass function, stellar content and dynamical state of UCDs in the Fornax cluster. Thanks to radial velocity membership assignment of ~950 globular clusters (GCs) and UCDs in the core of Fornax, the shape of their mass function is well constrained. It is consistent with the 'standard' Gaussian mass function of GCs. Our recent simulations on the disruption process of nucleated dwarf galaxies in cluster environments showed that ~40% of the most massive UCDs should originate from nuclear star clusters. Some Fornax UCDs actually show evidence for this scenario, as revealed by extended low surface brightness disks around them and onsets of tidal tails. Multi-band UV to optical imaging as well as low to medium resolution spectroscopy revealed that there exist UCDs with youngish ages, (sub-)solar [alpha/Fe] abundances, and probably He-enriched populations.