Research Overview

connecting local star-forming galaxies to the physics of reionization

ORCID
NASA/ADS Library
My CV

My research investigates how stars and galaxies shape their surrounding environments across cosmic time. I focus on the interstellar medium (ISM) and the conditions that allow galaxies to release energetic radiation capable of ionizing hydrogen in the early universe. By combining UV to mid-infrared spectroscopy from HST/COS and JWST/MIRI, I study how feedback, geometry, and metallicity regulate the escape of ionizing photons from star-forming galaxies.

Main Themes
  • Ionizing photon escape and extreme emission line galaxies: I use nearby, low-metallicity galaxies as laboratories for understanding how galaxies at z > 6 contributed to cosmic reionization. Through absorption-line diagnostics, emission-line ratios, and kinematic modeling, I test empirical predictors of Lyman-continuum (LyC) escape — such as LIS covering fractions, O₃₂, and Lyα velocity structure — and evaluate how they scale with global galaxy properties.
  • Multiphase ISM structure and stellar feedback: Star formation drives turbulence, outflows, and ionization fronts that shape the neutral and ionized gas around young clusters. Using spatially resolved observations from JWST/MIRI and ground-based IFUs, I trace the structure of ionized, molecular, and dust-bearing phases to study how stellar winds, radiation, and supernovae carve channels for LyC leakage.
  • Direct-method abundances and local enrichment: Metallicity and ionization balance are key to understanding energy regulation in galaxies. By mapping auroral lines and mid-IR fine-structure lines, I derive Tₑ, nₑ, and direct metallicities, revealing whether metals are well mixed or localized around massive star clusters.
  • Tools & pipelines: I am developing a PSF-mitigation pipeline for MIRI/MRS observations of extended sources that will enable spatial mapping.
Selected Publications
Parker, Berg, Gazagnes, et al. 2024
CLASSY XI: Tracing Neutral Gas Properties using UV Absorption Lines and 21-cm Observations
Parker, Berg, Chisholm, et al. 2026
CLASSY XIII: Cutting through the Clouds – Comparing Indirect Tracers of Ionizing Photon Escape
Parker, Berg, Jaskot & Rogers 2026
Mapping Ionizing Emission in Nearby Low-Metallicity Galaxies with MIRI/MRS In Prep.

UV/optical/radio/IR spectroscopy • ISM/CGM physics • Ionizing photon escape • Stellar feedback • Low-metallicity galaxies • JWST + HST observations • IFU analysis • Photoionization modeling • Galaxy evolution and reionization