Comparisons of the emission scale lengths (Mg II in purple and [O II] in green) and the O₃₂ ratios (top left), Hβ equivalent widths (top middle), metallicities (top right), UV half-light radii (bottom left), and H I covering fractions (bottom right). Upper limit values are shown with arrows. The Kendall correlation coefficient (τ) for every pair of variables and the corresponding false-positive probability that the correlation is real (p) are given for both emission lines in the top right corners following the same color coding as the data points (Akritas & Siebert 1996; Flury et al. 2022b, see Sect. 3.4).