Star formation rate per unit dense gas mass for bound gas and gas with a fixed density threshold. Left: M_AV>8 derived from Herschel column density maps above N(H₂) = 7.4 × 10²¹ cm⁻². The cloud mass M_cloud is calculated by integrating all cloud mass above A_V = 1. The blue circles show the relationship based on M_sgb from the N-PDF method, and the orange hexagons show the relationship based on $M_{{\mathrm{A}}_{\mathrm{V}}>8}^{\text{Herschel}}$. The orange and blue shaded regions correspond to the regimes with 1σ data scatters in linear least-squares fittings. Right: same as the left panel, but for the $M_{{\mathrm{A}}_{\mathrm{V}}>8}^{2\mathrm{M}\mathrm{A}\mathrm{S}\mathrm{S}+\text{Herschel}}$ case.