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L. J. Bartholomew (UNC-CH), N. Caldwell (SAO), J. A. Rose, A. E. Gaba (UNC-CH)
Galaxies in rich clusters with z>0.3 are known to have a much higher fraction of photometrically blue galaxies than their nearby counterparts. This raises the important question of what environmental effects can cause the termination of star formation between z=0.3 and the present. The star formation may be truncated due to ram-pressure stripping, or the gas in the disk may be depleted by a major starburst caused by some external perturbation. In order to resolve this issue, surface photometry was carried out for a total of 78 galaxies in the cluster Cl1358+62, at z=0.33, using two color images from the Hubble Archive. These galaxies were divided into two categories based on spectroscopic criteria: 27 are type "E+A" (i.e. strong Balmer lines, with no visible emission), while the remaining 51 are in the control sample with normal spectra. Radial color profiles were then produced to see if the "E+A" galaxies show bluer nuclei in relation to their surrounding disks. Specifically, a linear gradient was fit to the radial color profile of each galaxy. We find that the "E+A" galaxies on average have slightly bluer nuclei than the normals (which have flat gradients or slightly redder nuclei). A Kolmogorov-Smirnov two-sample test has been applied to the two sets of color gradients. The test rejects the hypothesis that both the "E+A" and normal samples are drawn from the same parent distribution at the 97% confidence level. This result favors the centralized star formation scenario as opposed to the truncated disk picture.