Hyper Suprime-Cam Low Surface Brightness Galaxies II: A Hubble Space Telescope Study of the Globular Cluster Systems of Ultra-Diffuse Galaxies in Groups

TL;DR

This study uses Hubble Space Telescope data to analyze globular cluster systems in ultra-diffuse galaxies across different environments, revealing diverse GC populations and potential correlations with galaxy properties.

Contribution

It expands the sample of UDGs with characterized GC populations in group environments and compares their properties across various environments, highlighting new trends.

Findings

Some UDGs have excess GCs similar to higher surface brightness galaxies.

Cluster UDGs tend to have higher GC abundances.

Possible correlations between GC abundance, stellar mass, and galaxy size.

Abstract

We increase the sample of ultra diffuse galaxies (UDGs) in lower density environments with characterized globular cluster (GC) populations using new Hubble Space Telescope observations of nine UDGs in group environments. While the bulk of our UDGs have GC abundances consistent with normal dwarf galaxies, two of these UDGs have excess GC populations. These two UDGs both have GC luminosity functions consistent with higher surface brightness galaxies and cluster UDGs. We then combine our nine objects with previous studies to create a catalog of UDGs with analyzed GC populations that spans a uniquely diverse range of environments. We use this catalog to examine broader trends in the GC populations of low stellar mass galaxies. The highest GC abundances are found in cluster UDGs, but whether cluster UDGs are actually more extreme requires study of many more UDGs in groups. We find a possible positive correlation between GC abundance and stellar mass, and between GC abundance and galaxy size at fixed stellar mass. However, we see no significant stellar-mass galaxy-size relation, over our limited stellar mass range. We consider possible origins of the correlation between GC abundance and galaxy size, including the possibility that these two galaxy properties are both dependent on the galaxy dark matter halo, or that they are related through baryonic processes like internal feedback.