We have obtained spectra for 62 galaxies in seven dense Butcher-Oemler (BO) clusters with redshifts 0.2 <= z <= 0.38. We combined them with data from the literature and examined the Butcher-Oemler effect. (1) The "color" of a galaxy measured by BO's photometry in redshifted bandpasses is generally consistent with the observed galaxy spectrum when compared with low-redshift red (E-S0) and blue (spiral) galaxies. The BO photometry distinguishes between galaxies with different spectra if they are within {DELTA}z ~ +/-0.1 of the mean cluster redshift. (2) We calculate df_b_/dz = 0.60 +/- 0.06 for the slope of the Butcher-Oemler effect. This is consistent with BO's photometric estimate df_b_/dz = 0.52, and is significantly different from zero at better than the 99.5% confidence level. (3) The velocity dispersions for these clusters are large in comparison with low-z rich clusters and show an unexpectedly large range of values. A simple virial analysis of the cluster parameters predicts a range substantially smaller than that observed. (4) The surface density of galaxies in the sample clusters shows a marked difference above and below z ~ 0.2. These results suggest that the BO sample does not consist of morphologically similar clusters observed over a range of redshifts. (5) The correlation between blue galaxy fraction and cluster velocity dispersion is strong but cannot be interpreted unambiguously in terms of stripping or starburst activity which might result from the dense cluster environment.
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Newberry et al. (1988) studied this question.