Intermediate-age Globular Clusters in Four Galaxy Merger Remnants

TL;DR

This study combines optical and infrared photometry to analyze globular cluster populations in four galaxy remnants, revealing intermediate-age clusters that align with their merger histories.

Contribution

It introduces a method of combining multi-band photometry with toy models to identify intermediate-age globular clusters in merger remnants.

Findings

Detection of intermediate-age (1-2 Gyr) globular clusters in all four galaxies.

Globular cluster ages are consistent with the galaxies' estimated merger ages.

Evidence supports the link between galaxy mergers and the formation of new globular clusters.

Abstract

We present the results of combining Hubble Space Telescope optical photometry with ground-based Ks-band photometry from the Gemini imagers NIRI and FLAMINGOS-I to study the globular-cluster populations in four early-type galaxies that are candidate remnants of recent mergers (NGC1700, NGC2865, NGC4382, and NGC7727). These galaxies were chosen based on their blue colors and fine structure, such as shells and ripples that are indicative of past interactions. We fit the combined VIKs globular-cluster data with simple toy models of mixed cluster populations that contain three subpopulations of different age and metallicity. The fits, done via Chi-square mapping of the parameter space, yield clear evidence for the presence of intermediate-age clusters in each galaxy. We find that the ages of 1-2 Gyr for these globular-cluster subpopulations are consistent with the previously estimated merger ages for the host galaxies.