Spatially resolved [OIII]/Hβ ratio maps. A general trend of higher values of this ratio along the EELR is observed, while the ratio is lower closer to the nucleus. This suggests that near the nucleus, the [OIII] emission has already declined, but this fading has not yet reached the outer regions because of the large extension of the clouds. This is consistent with the hypothesis that EELRs are “ionization echoes”.