Globular Cluster Systems and their Host Galaxies: Comparison of Spatial Distributions and Colors

TL;DR

This study compares the spatial distributions and colors of globular cluster systems and their host galaxies, revealing correlations and differences that inform galaxy formation theories.

Contribution

It provides a detailed comparison of GC spatial and color distributions across different galaxy types, highlighting their alignment or divergence from host galaxy properties.

Findings

Elliptical GCs align with host galaxy light in ellipticals.

S0 galaxy GCs are circular, contrasting with flattened galaxy light.

Significant color gradients found in NGC 4594's GC subpopulations.

Abstract

We present a study of the spatial and color distributions of four early-type galaxies and their globular cluster (GC) systems observed as part of our ongoing wide-field imaging survey. We use $BVR$ KPNO-4m+MOSAIC imaging data to characterize the galaxies' GC populations, perform surface photometry of the galaxies, and compare the projected two-dimensional shape of the host galaxy light to that of the GC population. The GC systems of the ellipticals NGC 4406 and NGC 5813 both show an elliptical distribution consistent with that of the host galaxy light. Our analysis suggests a similar result for the giant elliptical NGC 4472, but a smaller GC candidate sample precludes a definite conclusion. For the S0 galaxy NGC 4594, the GCs have a circular projected distribution, in contrast to the host galaxy light which is flattened in the inner regions. For NGC 4406 and NGC 5813 we also examine the projected shapes of the metal-poor and metal-rich GC subpopulations and find that both subpopulations have elliptical shapes that are consistent with those of the host galaxy light. Lastly, we use integrated colors and color profiles to compare the stellar populations of the galaxies to their GC systems. For each galaxy, we explore the possibility of color gradients in the individual metal-rich and metal-poor GC subpopulations. We find statistically significant color gradients in both GC subpopulations of NGC 4594 over the inner $\sim 5$ effective radii ($\sim 20$ kpc). We compare our results to scenarios for the formation and evolution of giant galaxies and their GC systems.