The Fornax 3D project: Globular clusters tracing kinematics and metallicities

TL;DR

This study uses MUSE spectroscopy to analyze 722 globular clusters in 32 Fornax cluster galaxies, revealing their kinematic behaviors and metallicity distributions, which shed light on galaxy evolution and assembly processes.

Contribution

It provides the first extensive spectroscopic analysis of GCs in the inner regions of multiple galaxies within the Fornax cluster, highlighting their kinematic and metallicity properties.

Findings

GC systems show signatures of rotation.

Red GCs follow the host galaxy's metallicity profile.

Blue GCs are more metal-poor with a wide metallicity spread.

Abstract

Globular clusters (GCs) are found ubiquitously in massive galaxies and due to their old ages, they are regarded as fossil records of galaxy evolution. Spectroscopic studies of GC systems are often limited to the outskirts of galaxies, where GCs stand out against the galaxy background and serve as bright tracers of galaxy assembly. In this work, we use the capabilities of the Multi Unit Explorer Spectrograph (MUSE) to extract a spectroscopic sample of 722 GCs in the inner regions ($\lesssim 3 R_\text{eff}$) of 32 galaxies in the Fornax cluster. These galaxies were observed as part of the Fornax 3D project, a MUSE survey that targets early and late-type galaxies within the virial radius of Fornax. After accounting for the galaxy background in the GC spectra, we extracted line-of-sight velocities and determined metallicities of a sub-sample of 238 GCs. We found signatures of rotation within GC systems, and comparing the GC kinematics and that of the stellar body shows that the GCs trace the spheroid of the galaxies. While the red GCs prove to closely follow the metallicity profile of the host galaxy, the blue GCs show a large spread of metallicities but they are generally more metal-poor than the host.