2004MNRAS.348..515G

We have investigated the redshift evolution of the colour-clustercentric radius relation and the morphology-clustercentric radius relation in three redshift bins, 0.02 ≤z ≤ 0.14, 0.14 < z ≤ 0.20 and 0.20 < z ≤ 0.30, using a homogeneous sample of 736 galaxy clusters selected from the Sloan Digital Sky Survey. Both the relations are well-defined in all the redshift bins; the fraction of blue/late-type galaxies increases toward the outside of clusters. Blue/late-type galaxy fractions are found to decrease with decreasing redshift at any clustercentric radius. The trend is consistent with the Butcher-Oemler effect and the morphological Butcher-Oemler effect. In addition, we find that colour (spectral) evolution is almost completed by z ∼ 0.2, whereas morphological evolution continues to the present day. The colour-radius relation is smooth in all the redshift bins, while the morphology-radius relation has a break only in the highest redshift bin. It is also found that fractions of blue late-type galaxies decrease mostly between the highest and the intermediate-redshift bins, while the fraction of red late-type galaxies continuously decreases with decreasing redshift through all redshift bins. These results are consistent with the interpretation that the time-scale of the colour (spectral) evolution is shorter than that of the morphological evolution. It is suggested that red-late-type galaxies in the middle of the transformation are observed as passive spiral galaxies.