Modelling chemical abundance distributions for dwarf galaxies in the Local Group: the impact of turbulent metal diffusion

Abstract

We investigate stellar metallicity distribution functions (MDFs), including\nFe and ${\\alpha}$-element abundances, in dwarf galaxies from the Feedback in\nRealistic Environments (FIRE) project. We examine both isolated dwarf galaxies\nand those that are satellites of a Milky Way-mass galaxy. In particular, we\nstudy the effects of including a sub-grid turbulent model for the diffusion of\nmetals in gas. Simulations that include diffusion have narrower MDFs and\nabundance ratio distributions, because diffusion drives individual gas and star\nparticles toward the average metallicity. This effect provides significantly\nbetter agreement with observed abundance distributions of dwarf galaxies in the\nLocal Group, including the small intrinsic scatter in [${\\alpha}$/Fe] vs.\n[Fe/H] (less than 0.1 dex). This small intrinsic scatter arises in our\nsimulations because the interstellar medium (ISM) in dwarf galaxies is\nwell-mixed at nearly all cosmic times, such that stars that form at a given\ntime have similar abundances to within 0.1 dex. Thus, most of the scatter in\nabundances at z = 0 arises from redshift evolution and not from instantaneous\nscatter in the ISM. We find similar MDF widths and intrinsic scatter for\nsatellite and isolated dwarf galaxies, which suggests that environmental\neffects play a minor role compared with internal chemical evolution in our\nsimulations. Overall, with the inclusion of metal diffusion, our simulations\nreproduce abundance distribution widths of observed low-mass galaxies, enabling\ndetailed studies of chemical evolution in galaxy formation.\n