Correlation between EW₈₆₂₁ and dust reddening for 2957 cases with E(BP − RP) from Andrae et al. (2023) shown in the upper panel and for 4656 cases with A_v from Green et al. (2019) shown in the lower panel. The color of the scattered points represents their number density estimated by the Gaussian KDE. The red dots and their color bars are the median values and the standard deviations calculated in each EW₈₆₂₁ bin with a step of 0.05 Å. The linear fits to EW₈₆₂₁ and dust reddening from previous works are overplotted as dashed lines: magenta for GFPR, black and red for GDR3, and blue for AS 23.