The Landscape of Galaxy Clusters at Low Redshift
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white-lvwhite-phd-physics-2026-thesis.pdf
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Author(s)
White, Laurel V.
Advisor(s)
McDonald, Michael A.
Date Issued
May 2026
Publisher
Massachusetts Institute of Technology
Abstract
As the endpoint of hierarchical structure formation, galaxy clusters allow us to probe physics on some of the largest scales. Observations of the intracluster medium (ICM) reveal insights about galaxy evolution, dark matter, and powerful outbursts from supermassive black holes called active galactic nuclei (AGN). In this work, I present the first analyses of the Cluster Evolutionary Reference Ensemble At Low-z (CEREAL)---a sample of 169 low-redshift (low-z) galaxy clusters identified using Planck and followed up in the X-ray with Chandra. It is subdivided into two mass bins to allow for tests of mass trends. The selection relies on the thermal Sunyaev-Zel'dovich (SZ) effect, which is largely unbiased to cluster cooling state as compared to an X-ray flux-selected sample. Therefore, the CEREAL sample is ideal for providing clean reference statistics to anchor evolutionary studies of clusters at low redshifts in an era where our observational capabilities are taking us to increasingly higher redshifts. The first of these analyses is a multiwavelength study of Abell 1885, which houses an X-ray-bright, highly-accreting AGN in its central galaxy. The work examines the relationship between star formation and mechanical black hole feedback in the ICM, finding evidence for two distinct timescales for the AGN duty cycle and the dissipation of energy from the AGN into the large-scale ICM. I then pivot to a population-level morphological characterization of the CEREAL sample using X-ray flux images. I provide constraints on the fractions of cool-core clusters, dynamically disturbed systems, and those housing X-ray-bright central AGN. I demonstrate the good agreement between the CEREAL constraints and those obtained from other SZ-selected samples as well as the differences between CEREAL and X-ray-selected samples. Finally, I describe a detailed thermodynamic analysis of the CEREAL sample using X-ray spectroscopy. This includes representative temperature, pressure, and entropy profiles and the best constraints to date on the central cooling properties of low-z galaxy clusters.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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