Top: observed molecular fraction (solid curve) and theoretical one (dashed), obtained with the prescription of Eq. (B.6) from the displayed gaseous and stellar profiles (dotted). Middle: observed (solid curves) vs. theoretical (dashed curves) profiles of HI and H₂; the latter are obtained from the observed gas profile and the theoretically evaluated molecular fraction f₂ (both in the top panel), as Σ(H₂) = f₂x Σ_G/1.4 and Σ(HI) = (1 − f₂)Σ_G/1.4. Bottom: observed SFR profiles in the MW disk, vs. a theoretical SFR (dashed) curve), obtained from the theoretical profile of the molecular gas in the middle panel.