A framework for empirical galaxy phenomenology: the scatter in galaxy ages and stellar metallicities

• Published in: Monthly notices of the Royal Astronomical Society Vol. 448; no. 2; pp. 1430 - 1445
• Main Authors: Muñoz, Joseph A., Peeples, Molly S.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01.04.2015
• Subjects: Age; Astronomy; Empirical analysis; Iron; Mathematical analysis; Metallicity; Phenomenology; Scatter; Star & galaxy formation; Star formation; Stars & galaxies; Stellar mass; Symbols; galaxies: dwarf; galaxies: formation; galaxies: abundances; galaxies: evolution
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv048

We develop a theoretical framework that extracts a deeper understanding of galaxy formation from empirically derived relations among galaxy properties by extending the main-sequence integration method for computing galaxy star formation histories. We properly account for scatter in the stellar mass–star formation rate relation and the evolving fraction of passive systems and find that the latter effect is almost solely responsible for the age distributions among z ∼ 0 galaxies with stellar masses above ∼1010 M⊙. However, while we qualitatively agree with the observed median stellar metallicity as a function of stellar mass, we attribute our inability to reproduce the distribution in detail largely to a combination of imperfect gas-phase metallicity and α/Fe ratio calibrations. Our formalism will benefit from new observational constraints and, in turn, improve interpretations of future data by providing self-consistent star formation histories for population synthesis modelling.