Ratio of inferred wind and ISM metallicities Z_w/Z_g plotted against virial velocity V_circ. Also shown (with arbitrary scaling) is the shape of Bayesian ζ_w as also plotted in Fig. 2; it is clearly not a power law, thus the different power-law forms of η_w introduce inflections in Z_w/Z_g. Left panel: as indicated in the legend, different trends of Z_w/Z_g are inferred by dividing the fitted form of ζ_w (see Eq. (22)) by various scalings of η_w (see text for more details). The shaded regions correspond to the trends allowed by the two different Bayesian estimates of ζ_w according to the different Δη priors. Right panel: broken-power law trend for η_w found by Muratov et al. (2015) is shown as a solid heavy (gray) curve, where the inflection at V_circ = 60 km s⁻¹ corresponds to a sharp decrease of Z_w/Z_g (see text for more details). The short-dashed (dark-blue) curve shows the relation found by Mitchell et al. (2020), in the low-mass regime where stellar feedback dominates, and the long-dashed (blue) curve shows the observed relation derived by Chisholm et al. (2018).