S/N of Hβ as a function of the corrected SFR surface density. The vertical red dashed line indicates S/N_Hβ = 50, while the blue dashed line is the selection criterion of H II region-dominated spaxels for the MaNGA survey proposed by Zhang et al. (2017). The two green horizontal lines locate Σ_SFR, cor = 0.01 and 0.1 M_⊙yr⁻¹kpc⁻², respectively. The three percentages suggest the fractions of spaxels within each Σ_SFR, cor bin. Spaxels between the green lines are adopted as the subsample to fit the slopes of the nebular dust attenuation curve. The underlying gray map and cyan contours are the same as those in Fig. 1.