Universal Blacksmith: How to Decipher a Galaxy's Formation History from Stellar Metal Abundances

Metals play an essential role in a galaxy's life, as they are important ingredients for the cooling processes in the gas component, but also influence the lifetimes of the stars and encode information about the star formation histories of galaxies. However, most of our understanding on how to interpret the observed metallicities to decipher a galaxy's formation history so far originates from closed box models or idealized formation scenarios. Using the cosmological volume Magneticum simulations and its successors, I will present how metallicities evolve in realistic galaxy formation pathways that are dominated by accretion, merging, and feedback cycles. I will show that high levels of alpha elements in the stars reflect galactic formation histories dominated by extreme star formation bursts short enough to allow only enrichment by supernovae Type II, while a continuous star formation history imprints in a higher iron abundance reaching up to super solar values. I will demonstrate that these abundances can even be used in quiescent galaxies to infer their quenching times, and the number of star formation episodes. Furthermore, I will discuss the importance of high-resolution observations of the metal content to even locate different epochs of star formation radially. Finally, I find that the alpha abundance can tightly predict both the formation and assembly redshift, i.e., the median age of the stars, and when half of them first assembled into a single progenitor galaxy.