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 |
| Zoom |