Globular Cluster Systems of Early-type Galaxies in Low-density Environments

TL;DR

This study compares globular cluster systems in early-type galaxies from low- and high-density environments, revealing that galaxy mass primarily influences GC properties while environment has a secondary effect, with some differences in metallicity and age.

Contribution

It provides a comparative analysis of GC systems in different environments, highlighting the dominant role of galaxy mass and the secondary influence of environment on GC formation.

Findings

GC mean colours are bluer in low-density environments.

Colour bimodality disappears faster in lower luminosity galaxies.

GC properties correlate strongly with host galaxy luminosity.

Abstract

Deep images of 10 early-type galaxies in low-density environments have been obtained with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The global properties of the globular cluster (GC) systems of the galaxies have been derived in order to investigate the role of the environment in galaxy formation and evolution. Using the ACS Virgo Cluster Survey (ACSVCS) as a high-density counterpart, the similarities and differences between the GC properties in high- and low-density environments are presented. We find a strong correlation of the GC mean colours and the degree of colour bimodality with the host galaxy luminosity in low-density environments, in good agreement with high-density environments. In contrast, the GC mean colours at a given host luminosity are somewhat bluer (\Delta(g-z) ~ 0.05) than those for cluster galaxies, indicating more metal-poor (\Delta[Fe/H] ~ 0.10-0.15) and/or younger (\Delta age > 2 Gyr) GC systems than those in dense environments. Furthermore, with decreasing host luminosity, the colour bimodality disappears faster, when compared to galaxies in cluster environments. Our results suggest that: (1) in both high- and low-density environments, the mass of the host galaxy has the dominant effect on GC system properties, (2) the local environment has only a secondary effect on the history of GC system formation, (3) GC formation must be governed by common physical processes across a range of environments.