Example of galaxy quenching stages defined by K21 through visual inspection of the W_Hα distribution (from top left to bottom right): star-forming, quiescent-nuclear-ring, centrally quiescent, mixed, nearly retired, and fully retired. The colour bar separates the regions of the W_Hα maps (e.g. Sánchez et al. 2014, K21) into: star-forming (W_Hα > 6 Å), mixed (3 < W_Hα ≤ 6 Å), and retired (W_Hα ≤ 3 Å). The dashed contours correspond to half of the galaxy’s effective radius (R_e), while the continuous contours indicate 1, 2, and 3R_e. See Sect. 1 and K21 for more details.