Two-dimensional emission line classification ‘QuestNA’ of our sample of galaxies (see Sect. 3). The rows represent the quenching stages of the galaxies: star-forming, quiescent-nuclear-ring, centrally quiescent, mixed, nearly retired, and fully retired with increasing ‘retired/star-forming regions’ ratio of the galaxy from top to bottom. The columns reflect the level of galaxy nuclear activity: non-active, weak, and strong AGN from left to right. Each panel of the scheme shows the W_Hα map of the galaxy, where the dashed contour indicates 0.5 of the effective radius, and the continuous contours correspond to 1, 2, and 3R_e, respectively. The colour bar of the W_Hα maps divides the regions of the galaxy into star-forming (W_Hα > 6 Å), retired (W_Hα ≤ 3 Å), and mixed (3 Å < W_Hα ≤ 6 Å). There are 14 emission-line classes of QuestNA instead of 18, because two of the quenching stages, centrally quiescent and fully retired, are only non-active galaxies, which by definition are fully retired in the central regions.