Connecting Chemical Enrichment with Resolved Star Formation Histories

Abstract: We present a new framework for modeling the chemical enrichment histories of galaxies by integrating the chemical evolution with resolved star formation histories (SFHs) derived from color-magnitude diagrams. This novel approach links the time evolution of the metallicity of the star-forming ISM to the cumulative stellar mass formed in the galaxy, enabling a physically motivated, self-consistent description of chemical evolution. We apply this methodology to four isolated, gas-rich Local Group dwarf galaxies -- WLM, Aquarius, Leo A, and Leo P -- using deep HST and JWST imaging. For WLM, Aquarius, and Leo A, we independently validate our metallicity evolution results using ages and metallicities of individual red giant stars with spectroscopic measurements, finding good agreement. We quantify systematic uncertainties by repeating our analysis with multiple stellar evolution and bolometric correction libraries. We then compare the observed chemical enrichment histories to predictions from the TNG50 and FIREbox cosmological hydrodynamic simulations and the Galacticus semi-analytic model. We find that the enrichment history of WLM is best reproduced by the FIREbox simulation, while TNG50 and Galacticus predict higher metallicities at early times. Our results suggest that differences in stellar feedback and metal recycling prescriptions drive significant variation in the predicted chemical enrichment of dwarf galaxies, particularly at early times. This work demonstrates the power of combining resolved SFHs with physically motivated chemical evolution models to constrain galaxy formation physics and highlights the need for further observational and theoretical studies of metal retention and recycling in low-mass dwarf galaxies.