SED Fitting of Globular Clusters in NGC 4874: Masses and Metallicities

TL;DR

This study uses multi-filter HST photometry to perform SED fitting on globular clusters in NGC 4874, deriving their metallicities, masses, and mass-to-light ratios, providing insights into their properties in a distant galaxy.

Contribution

First application of multi-filter SED fitting to GCs in a distant galaxy using HST data, enabling detailed metallicity and mass estimates.

Findings

Derived metallicities and masses for 29 GCs in NGC 4874.

Estimated mass-to-light ratios between 2 and 4 for the GCs.

Confirmed consistency of results with known properties of Milky Way GCs.

Abstract

In most nearby galaxies, photometry of the integrated light of their globular clusters (GCs) has been obtained in only two filters, yielding just a single color index. However, NGC 4874, the brightest central galaxy in the Coma cluster, now has Hubble Space Telescope (HST) photometry available in ten filters, giving us a special opportunity to test SED fitting procedures on GCs in distant galaxies. We fitted 29 of the brightest GCs with a library of SEDs from E-MILES and calculated the best-fit metallicity and mass of each cluster. Using the fitted masses and luminosities derived from the reddest magnitudes, in the flat portion of the GC spectrum, we also calculated inferred mass-to-light ratios for our sample GCs; these were in the range (M/L) $\simeq 2 - 4$, slightly larger than the average values for Milky Way GCs but within the conventional range.