Non-solar scaled abundances for massive stars: the chemical abundance breakthrough for galaxy evolution

Kathryn Grasha

Australian National University

Our current understanding of galaxy evolution hinges on the assumption that the universe has Solar-scaled metallicity abundances, which is not applicable outside our Solar System. This prohibits progress in understanding how the distribution of the metals in stars are recycled into the interstellar gas of galaxies throughout cosmic time. I will present the first set of massive stellar evolutionary tracks, computed by modifying the Modules for Experiments in Stellar Astrophysics (MESA) 1D stellar evolution package, to fit the Galactic Concordance abundances for hot massive Main-Sequence stars. These models are based on observed metal abundances in HII regions using the Galactic Concordance scaling system, which allows us, for the first time, for us to accurately compare stellar observations against models that are not constrained solely against a single star, the Sun. The evolutionary tracks for our Galactic Concordance abundance scaling provides a more physically motivated approach than simple uniform abundance scaling with metallicity for the analysis of HII regions and has considerable implications in determining nebular emission lines and metallicity. We find that the ionising photon output differs by up to 2dex from Solar-scaled stars for ages up to 5 Myr, which has broad implications for our interpretation of emission line spectra from observations. As the surface enhancement of elements in massive rotating stars have broad impact on the ionizing spectra of high-redshift, low-metallicity galaxies, stellar models with realistic, variable metallicities need to be considered to accurately model and predict the properties of galaxies across cosmic time.

Date: Jeudi, le 24 mars 2022
Heure: 11:30
Lieu: Université de Montréal