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Author ORCID Identifier

https://orcid.org/0009-0009-1792-7199

Date Available

8-11-2026

Year of Publication

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Arts and Sciences

Department/School/Program

Physics and Astronomy

Faculty

Ryan L. Sanders

Faculty

Yuanyuan Su

Abstract

Understanding galaxy formation and evolution requires tracing how baryons cycle between stars, gas, and the interstellar medium (ISM) across cosmic time. The efficiency of star formation, the buildup of metals, and the regulation of gas inflows and outflows are governed by evolving physical conditions within galaxies and their environments. My thesis investigates how the ionized ISM, star formation histories, and environmental processes have shaped galaxy evolution over the past ∼ 12 Gyr. The primary focus of this work is the evolution of the physical conditions of ionized gas in galaxies, including gas-phase metallicity and ionization state. Using new and archival spectroscopic observations from Keck and JWST, we measure nebular emission-line diagnostics across a wide redshift range (z ∼ 1−4) to quantify how metallicity scaling relations, excitation conditions, and ionization parameters evolve with stellar mass and star formation rate. To connect integrated galaxy properties to internal structure, we model spatially resolved star formation histories using HST and JWST imaging, investigating how star formation and chemical enrichment vary within galaxies. This resolved perspective provides insight into how gas inflows, feedback processes, and structural evolution shape radial gradients and star formation efficiencies. In addition, we explore environmental influences on galaxy evolution through a detailed study of a nearby (z ∼ 0.06) anomalous blue galaxy cluster lacking a detectable intracluster medium. Using multi-wavelength observations from XMM-Newton, Subaru-HSC, IRAM, and the VLA, we investigate how the absence of a hot intracluster medium affects star formation activity, gas content, and feedback processes in cluster galaxies. Together, these studies provide a multi-scale view of baryon cycling, linking ionized gas conditions, chemical enrichment, internal galaxy structure, and environmental effects. This work advances our understanding of how galaxies regulate their gas supply and build up stellar mass across cosmic history.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.384

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