Wednesday

The cosmic star-formation rate density (SFRD) and cosmic metal density (ZD) in the Universe are key diagnostics for understanding galaxy evolution. Combined, they encode the relative significance of all the main evolutionary processes driving galaxy formation, including gas accretion, star formation, metal enrichment, and outflows driven by SN & AGN feedback.

In this talk, I will present brand new results from the TNG100, EAGLE, and L-GALAXIES 2020 cosmological simulations on the evolution of the SFRD and ZD from z=7 to 0. I will show that, while these simulations are able to reproduce either the observed SFRD or ZD, none is able to simultaneously match both. For example, some simulations are able to reproduce the high metal content observed in the neutral gas of damped Lyman-alpha systems at z~3-5 (e.g. Peroux & Howk 2020), but require cosmic star formation rates in excess of those currently observed (e.g. Madau & Dickinson 2014) to do so. These results demonstrate the huge importance of considering the ZD alongside the SFRD when studying galaxy evolution.

I will discuss how differences in the star formation, feedback, and chemical enrichment modelling in these three simulations contributes to their differing results, and will also highlight how potential biases in the observational SFRD and ZD measurements could contribute to their perceived incompatibility. These results will also be set in the context of up-coming observations from JWST, which will allow us to probe cosmic star formation and metallicity in high-redshift galaxies down to much lower levels than ever before.