SPECIAL GUEST SPEAKER
Dr Kathryn Grasha – Guest Speaker Friday 29th August 2025
Topic: Local Clues to a Cosmic Story: Reconstructing Galaxy Evolution from the Inside Out.
Dr. Kathryn Grasha is an observational astronomer at the Research School of Astronomy and Astrophysics at the Australian National University. Her research sheds light on the physics that governs how galaxies transform and evolve by tracing how oxygen atoms we breathe and the carbon we are made of formed across cosmic time. Dr. Grasha earned her PhD in 2018 from the University of Massachusetts and is now an ARC DECRA Fellow at ANU.
Abstract: Local Clues to a Cosmic Story: Reconstructing Galaxy Evolution from the Inside Out
Understanding how galaxies grow and evolve over cosmic time is a central challenge in astrophysics. My research focuses on the lifecycle of baryons — how gas becomes stars and is later recycled — by studying the chemical evolution of galaxies. I explore the link between individual star-forming regions and the global buildup of metals, using spatially resolved spectroscopy of H II regions to measure gas-phase abundances and star formation activity.
Crucially, interpreting nebular emission lines, the foundation for metallicity measurements at high redshift, requires accurate models of the stellar ionizing radiation field. Most current models are calibrated to Solar abundance patterns, which do not reflect the non-Solar chemical ratios observed in H II regions beyond the Milky Way.
This mismatch limits our ability to make robust comparisons across cosmic time. By anchoring emission-line diagnostics to realistic stellar and chemical environments, my work enables physically consistent comparisons between early chaotic galaxies and the ordered spirals we see today, laying the foundation for a unified understanding of galaxy evolution through the chemical fingerprints of stars and gas.
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