Description
We use a large, multicolor mosaic of HST WFPC2 images to measure the colors and morphologies of 194 spectroscopically confirmed members of the rich galaxy cluster CL 1358+62 at z=0.33. We study the color-magnitude (CM) relation as a function of radius in the cluster to a limit of 4.6' from the center, equivalent to 1.6h^-1^_50_Mpc. The intrinsic scatter in the rest-frame B-V CM relation of the elliptical galaxies is very small, ~0.022mag. The CM relation of the ellipticals does not depend significantly on the distance from the cluster center. In contrast, the CM relation for the S0 galaxies does depend on radius: the S0's in the core follow a CM relation similar to that of the ellipticals, but at large radii (R>0.7h^-1^_50_Mpc) the S0's are systematically bluer and the scatter in the CM relation approximately doubles, to ~0.043mag. The blueing of the S0's at large radii is significant at the 95% confidence level. These results imply that the S0 galaxies in the outer parts of the cluster have formed stars more recently than the S0's in the inner parts.
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