The SLUGGS Survey: Wide Field Imaging of the Globular Cluster System of NGC 4278

TL;DR

This study uses multi-instrument imaging and spectroscopy to analyze the globular cluster system of NGC 4278, revealing bimodality, colour gradients, and size variations linked to cluster properties and galaxy structure.

Contribution

It provides a detailed analysis of the globular cluster system of NGC 4278, including surface density, colour bimodality, and size relations, using combined imaging and spectroscopic data.

Findings

Globular cluster system is slightly more populous than average.

Clear bimodality in colour distribution with a blue tilt.

Negative radial colour gradients in both subpopulations.

Abstract

We use multi-pointing HST ACS and wide field Subaru Suprime-Cam imaging to study the globular cluster system of the L* elliptical galaxy NGC 4278. We have also obtained a handful of new globular cluster spectra with Keck/DEIMOS. We determine the globular cluster surface density profile and use it to calculate the total number of globular clusters, finding the system to be slightly more populous than average for galaxies of its luminosity. We find clear evidence for bimodality in the globular cluster colour distribution and for a colour-magnitude relation in the blue subpopulation (a 'blue tilt'). We also find negative radial colour gradients in both colour subpopulations of equal strength which are similar in strength to those reported in other galaxies. The sizes of NGC 4278's globular clusters decrease with redder colours and increase with galactocentric radius. The ratio of the sizes of blue to red globular clusters is independent of galactocentric radius demonstrating that internal effects are responsible for the size difference with colour.