Spatially-resolved total gas Schmidt relation (Σ_SFR and Σ_H I+H2). In each panel, blue dots with green error bars are the spatially-resolved data, and the solid black line shows the best-fit to the spatially-resolved data for all galaxies. We have assumed a Kroupa IMF and adopted a constant X(CO) factor = 2.0 × 10²⁰ cm⁻² (K km s⁻¹)⁻¹. Upper-left panel: no subtraction of diffuse background is done. The vertical dotted line corresponds to 10 M_⊙ pc⁻² around which atomic gas surface density saturates. Upper-right panel: the diffuse background is subtracted from the SFR tracers. The solid yellow line and the dashed red line denote star-formation relation from Elmegreen 2015 (E2015) and correspond to velocity dispersion (σ) of 6 km s⁻¹ and 11 km s⁻¹ respectively. Lower-left panel: the diffuse background is subtracted from the SFR tracers as well as from H I. Lower-right panel: the diffuse background is subtracted from the SFR tracers, HI and CO. The solid yellow solid line on lower panels corresponds to the star-formation relation based on a dynamical model from Elmegreen (2015) obtained at a constant scale height of H = 100 pc. See text in Sect. 5.1 for further details on models.