Left panel: dust-to-gas mass ratio within r₂₅ as a function of the morphological stage, from T = 1 to T = 10, assuming a constant X_CO (Bolatto et al. 2013). All gas types (atomic, molecular, total gas) are considered and separately plotted. Data of individual galaxies are shown in transparency: blue circles are dust/H₂, red squares dust/HI, green triangles dust/total gas. The large symbols represent the mean values (and their uncertainties) in bins of ΔT = 1, except for the types T = 8, 9, 10 that are binned together. The black lines are the linear fits of the trends. Right panel: same as left panel assuming a metallicity-dependent X_CO (Amorín et al. 2016).