Compact Stellar Systems as Tracers of Galaxy Evolution: Environmental Signatures in a Massive Galaxy Cluster

Author

• Richard Thomas Pomeroy, The University of Texas Rio Grande Valley

Date of Award

7-1-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Juan Madrid

Second Advisor

Matthew Benacquista

Third Advisor

Lucas Macri

Abstract

This thesis uses compact stellar systems (CSSs)—particularly globular clusters (GCs) and ultracompact dwarfs (UCDs)—as long-lived tracers of environmental processing in the dense core of the Coma Cluster. Using deep Hubble Space Telescope (HST)/ACS imaging, we analyze the spatial distributions, luminosity functions, color subpopulations, and azimuthal structure of CSS populations across the central ∼1 Mpc.

In the first study, we examine the bright end of the globular cluster luminosity function (GCLF) and the cluster-wide UCD distribution. We identify an excess of bright CSSs relative to an extrapolated GCLF and find that blue UCDs are more spatially extended than red UCDs, consistent with a composite UCD population that may include an environmentally produced contribution (e.g., stripped nuclei).

In the second study, we compare expected and observed GC populations for major Coma galaxies using two-dimensional Voronoi GC density maps. We identify several galaxies with depleted globular cluster systems (GCSs) and show that their projected GCS morphologies range from strongly asymmetric to nearly isotropic, highlighting degeneracies between recent stripping, older phase mixing, symmetric truncation, and intrinsic formation efficiency.

In the third study, we introduce a blue-GC fraction excess diagnostic and relate it to cluster-centric radius, dual-brightest cluster galaxy (BCG) influence, and the local GC density field. The strongest trends are linked to local GC density and BCG-related measures, implying that the Coma core is a structured, multi-scale environment rather than a smooth radially isotropic field.

Overall, the results show that environmental processing in Coma is local and population-dependent, acting most strongly on the extended blue GC component and coupling galaxy-halo transformation to the buildup of the intracluster CSS population.

Comments

Copyright 2026 Richard Thomas Pomeroy. All Rights Reserved. https://proquest.com/docview/3409019622

Recommended Citation

Pomeroy, R. T. (2026). Compact Stellar Systems as Tracers of Galaxy Evolution: Environmental Signatures in a Massive Galaxy Cluster [Doctoral dissertation, The University of Texas Rio Grande Valley]. ScholarWorks @ UTRGV. https://scholarworks.utrgv.edu/etd/2021