Depletion time of the dense molecular gas estimated from HCN, /Σ_SFR, as a function of the self-gravity of the gas, measured by the parameter b ≡ Σ_dense/σ², at different spatial scales (magenta circles and isodensity contours): 56 pc, namely the initial resolution of ALMA observations (left panel), 100 pc (middle panel), and 400 pc (right panel). A significant trend in as a function of b, identified in the middle and right panels, indicates a higher rate of SF per unit mass of dense gas for regions with stronger self-gravity. Values of ⟨b⟩ for the 100 pc and 400 pc apertures were derived from an intensity-weighted average of b evaluated at the Nyquist-sampled grid of points for each aperture. Values of were derived using a Gaussian-weighted average. Black circles show median , and error bars indicate the rms scatter in the bins. The green lines in the right panel identify the two regimes in the plot found by the MARS algorithm to fit the data using 400 pc as averaging scale. Vertical and horizontal error bars at the lower-right corner of each panel account for the typical uncertainties, which amount to ±0.13 dex and ±0.09 dex, respectively.