<scp>L-GALAXIES</scp> 2020: The evolution of radial metallicity profiles and global metallicities in disc galaxies
Robert M. Yates, Bruno Henriques, Jian Fu, Guinevere Kauffmann, P. Thomas, Qi Guo, Simon D. M. White, P. Schady
Abstract
ABSTRACT 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 ($Z_{\rm {g}}$) 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 $Z_{\rm {g}}$ 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 $Z_{\rm {g}}$ 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 $25\, {\rm M}_{\odot }$, reflecting recent theoretical and observational estimates, can also provide a good match to observed $Z_{\rm {g}}$ and Z* profiles at z = 0 in L-galaxies2020. However, this model version fails to reproduce an evolution in $Z_{\rm {g}}$ at fixed mass over cosmic time, or the magnesium abundances observed in the intracluster medium (ICM).