[O/Fe] - sSFR relation of galaxies

Abstract: Our knowledge of the star-forming metallicity of galaxies is primarily based on gas-phase oxygen abundance measurements. However, this may not allow to accurately describe differences in stellar evolution and feedback driven by variations in iron abundance. These two elements are produced by nucleosynthetic sources operating on different timescales, and the link between them is not straightforward.

In this talk I will discuss the origin of the [O/Fe] - specific star formation rate (sSFR) relation, which connects chemical abundances to galaxy formation timescales. This relation is followed by star-forming galaxies across redshifts according to cosmological simulations and basic theoretical expectations. Its apparent universality makes it suitable for trading the readily available oxygen for iron abundance where the latter cannot be measured. 

I will show that the average relation is determined by the relative iron production efficiency of core-collapse and type Ia supernovae and the delay time distribution of the latter - uncertain factors that could be constrained empirically with the [O/Fe] - sSFR relation. I will discuss observational constraints on this relation and show that they are broadly consistent with expectations, but are currently insufficient to inform the models. Finally, I will use the relation to show that star formation with the solar O/Fe ratio is rare throughout the cosmic history.

This seminar is organised by the Ursa Minor research group and is open to all.