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Title: Anchoring the Extragalactic Abundance Scale
Speaker: Kathryn Grasha
Affiliation: Australian National University
Room: Å101190
Time: 14:00-15:00
Abstract:
Cosmic chemical evolution is inferred almost entirely from emission lines of photoionised nebulae, yet the abundance scale underlying these diagnostics remains fundamentally uncertain. In this talk, I will present a program to establish absolute benchmarks for the extragalactic abundance scale by unifying stellar and nebular chemical measurements in HII regions located in the Magellanic Clouds and nearby universe galaxies. Using data from the WiFeS IFU spectrograph on the ANU 2.3m and the UVES spectrograph on the VLT, we directly connect precise stellar compositions to self-consistent modelling of the surrounding ionized gas.
By anchoring emission-line diagnostics to physically constrained abundances, we are calibrating the impact of stellar enrichment on nebular spectra and starting to provide robust reference standards for interpreting galaxy observations across cosmic time. This talk will show results from the first data release and discuss the initial findings and implications, representing a critical step toward placing galaxy evolution studies on a secure chemical foundation.