BPT diagram and corresponding stellar mass relations for the [O III]/Hβ and [N II]λ6584/Hα ratios based on the EDS-SF_sim stacked mock spectra. The top and middle panels show the [O III]/Hβ–stellar mass (i.e. the MEx diagnostic diagram, Juneau et al. 2011), and [N II]λ6584/Hα–stellar mass relations, respectively, with measurements from the stacked spectra in different stellar mass bins. The bottom panel displays the BPT diagram with symbols representing the positions of the stacked spectra for various mass bins. The black contours in all panels represent the EDS-SF_sim parent sample cut at H_E ≤ 26, and the black dashed curves in the top and middle panels represent its median relations.