Impact of varying R₂₁ and α_{¹²CO(1−0)} on the Kennicutt-Schmidt relation We compare the KS relation using three different ways of estimating the molecular gas mass, Σ_mol: (i) ¹²CO(1–0) and a radially interpolated α_{¹²CO(1−0)} derived for each galaxy (ii) ¹²CO(1–0) and a fixed α_{¹²CO(1 − 0)}^MW = 4.3 M_⊙ pc⁻²/(K km s⁻¹), and (iii) ¹²CO(2–1) and a fixed R₂₁ = 0.6 (and R₂₁ = 0.9 in M51; den Brok et al. 2022). The resulting KS index, N, is determined using an orthogonal distance regression (fit indicated by solid line) and indicated in each panel with its 1σ uncertainty. In addition, each panel also lists the Σ_SFR value (in log) at Σ_mol = 10 M_⊙ pc⁻², as derived from the linear fit. The KS coefficient, N, the Pearson’s correlation coefficient, p, and as the SFR surface density at a molecular gas mass surface density of 10 M_⊙ pc⁻² or the linear relationship are indicated in each panel as well. The grey shaded region shows the ±0.30 dex dispersion which is expected for a larger sample of galaxies (Bigiel et al. 2008; Leroy et al. 2013). The points, which represent the individual solution pixels, are color-coded by their difference (in dex) in Σ_mol to the molecular gas mass determined using method (iii), which is shown in the right panel. Squares indicate the central points (r ≤ 2 kpc).