NGC 6946: radial profiles of the main physical quantities with and without in calculations. First panels: (dark blue) show the total (solid) and gaseous (dashed) Toomre Q parameter. Second panels: (red) show the mass accretion rate Ṁ. Third panels: (blue) show the velocity dispersion profiles σ_disp (solid) with the observed HI moment-2 linewidth (Caldú-Primo et al. 2013; dotted). Fourth panels: (green) show the depletion (t_dep; solid) and viscous (t_vis; dashed) timescales. Fifth panel: (yellow) shows the CO-to-H₂ (α_CO; solid) and HCN-to-dense gas (α_HCN; dashed) conversion factors. Dotted lines correspond to the Galactic value of and the Gao & Solomon value .