Massive Star Clusters in Dwarf Galaxies

TL;DR

This paper investigates the properties and origins of globular clusters in dwarf galaxies, revealing their high specific frequencies, low metallicities, and implications for cluster formation and evolution models.

Contribution

It provides new insights into the initial mass function and chemical properties of globular clusters in dwarf galaxies, challenging existing self-enrichment scenarios.

Findings

High globular cluster specific frequencies in dwarf galaxies.

Metal-poor GCs constitute up to 25% of stars in some dwarfs.

Initial cluster mass function may have been more top-heavy.

Abstract

Dwarf galaxies can have very high globular cluster specific frequencies, and the GCs are in general significantly more metal-poor than the bulk of the field stars. In some dwarfs, such as Fornax, WLM, and IKN, the fraction of metal-poor stars that belong to GCs can be as high as 20%-25%, an order of magnitude higher than the 1%-2% typical of GCs in halos of larger galaxies. Given that chemical abundance anomalies appear to be present also in GCs in dwarf galaxies, this implies severe difficulties for self-enrichment scenarios that require GCs to have lost a large fraction of their initial masses. More generally, the number of metal-poor field stars in these galaxies is today less than what would originally have been present in the form of low-mass clusters if the initial cluster mass function was a power-law extending down to low masses. This may imply that the initial GC mass function in these dwarf galaxies was significantly more top-heavy than typically observed in present-day star forming environments.