2021MNRAS.503.4474Y

We present a modified version of the L-GALAXIES2020 semi-analytic model of galaxy evolution, which includes significantly increased direct metal enrichment of the circumgalactic medium (CGM) by supernovae (SNe). These more metal-rich outflows do not require increased mass-loading factors, in contrast to some other galaxy evolution models. This modified L-GALAXIES2020 model is able to simultaneously reproduce the gas-phase metallicity (Z_g) and stellar metallicity (Z_*) radial profiles observed in nearby disc galaxies by MaNGA and MUSE, as well as the observed mass - metallicity relations for gas and stars at z = 0 and their evolution back to z ∼ 2-3. A direct CGM enrichment fraction of ∼90 per cent for SNe-II is preferred. We find that massive disc galaxies have slightly flatter Z_g profiles than their lower-mass counterparts in L-GALAXIES2020, due to more efficient enrichment of their outskirts via inside-out growth and metal-rich accretion. Such a weak, positive correlation between stellar mass and Z_g profile slope is also seen in our MaNGA-DR15 sample of 571 star-forming disc galaxies, although below log₁₀(M_*/M_☉) ∼ 10.0 this observational result is strongly dependent on the metallicity diagnostic and morphological selection chosen. In addition, a lowered maximum SN-II progenitor mass of 25 M_☉, reflecting recent theoretical and observational estimates, can also provide a good match to observed Z_g and Z_* profiles at z = 0 in L-GALAXIES2020. However, this model version fails to reproduce an evolution in Z_g at fixed mass over cosmic time, or the magnesium abundances observed in the intracluster medium (ICM).