Redshifts in z~0.25 clusters

The wavelength range allows us to quantify the star formation activity by using the [OII] and the H{alpha} lines. This activity is examined in terms of the large-scale environment expressed by the clustercentric distance of the galaxies as well as on local scales given by the spatial galaxy densities. The suppression of the star-formation activity is observed at large clustercentric distances and low projected densities.

Galaxies with current star-formation show similar activity, regardless of the environment, Therefore, the decline of the star-formation activity inside the investigated clusters is driven mainly by the significant change in the fraction of active versus passive populations. This suggests that the suppression of the star-formation activity occurs on short timescales. We also detect a significant population of red star-forming galaxies whose colors are consistent with the red-sequence of passive galaxies.

They appear to be in an intermediate evolutionary stage between active and passive types.