Gradients of column densities of H₂, N_H2, as a function of Galactocentric radius (R_GC). The light blue dataset represents the column densities estimated using a constant gas-to-dust ratio (γ = 100), while the dark blue dataset shows the column densities calculated with a gas-to-dust ratio function of R_GC from Giannetti et al. (2017). Both datasets have been fitted with a linear regression. The 1σ error bars over the slope of the gradients are displayed for each fit. In the upper-right side of the plot, the Pearson correlation coefficient, ρ, is shown (only for the dark blue dataset).