Left panel: dust-to-gas mass ratio within r₂₅ as a function of the gas-phase metallicity assuming a constant X_CO (Bolatto et al. 2013). Symbols are as in Fig. 8. The large symbols are mean values in metallicity bins, with the bin sizes chosen to include comparable numbers of galaxies. The solid line is the linear fit to all the mean values of the dust-to-total gas mass ratio (big green triangles), while the dashed line is the linear fit to those excluding the high-metallicity bin. Right panel: same as left panel assuming a metallicity-dependent X_CO (Amorín et al. 2016).