﹩{[{\rm{MgFe}}]}^{{\prime} }﹩ vs. Mg_b/〈Fe〉 plane, where the grids are from the sMILES SSPs, which have been convolved to the same resolution. The thicker red arrow points to the direction of increasing metallicity, and the thinner red arrow points to the direction of increasing [α/Fe]. We show the relations in SSPs with two different IMFs: universal Kroupa (P. Kroupa 2001; blue dashed lines) and bimodal IMF (A. Vazdekis et al. 1996) with Γ = 2.8. The stellar age of both grids is set at 10 Gyr to reflect the old stellar population of our galaxies. The six data points are the values of two samples and three radial bins. (a) High σ_* (filled orange) and low σ_* (empty blue). (b) Compact (filled green) and extended (empty purple). The Jupyter notebook for reproducing this figure can be found here: ✎. This repository is also available on Zenodo (https://doi.org/10.5281/zenodo.17979404).