Correlations between CO luminosity concentration (C_CO) and molecular gas mass concentration (C_mol). Top panel:C_mol(α_CO[R]) derived based on α_CO(R), which is a function of radius and is set the same for all the galaxies (Eq. (6)). Bottom panel:C_mol(α_CO[Z, Σ_⋆]) computed based on α_CO[Z, Σ_⋆], which is a function of Z and Σ_⋆ and varies from galaxy to galaxy (Eq. (8)). The dashed lines mark the 1 : 1 relations.