The authors present the results of spectroscopic observations of three concentrated Abell clusters of galaxies at a redshift of 0.2: A223, A963, and A2111. The data confirm the blue galaxy fraction for these clusters determined photometrically by Butcher and Oemler. The blue galaxy population is dominated by galaxies whose spectra show features due to young and intermediate-age stars. The authors present evidence that these galaxies have undergone extensive bursts of star formation. They conclude that the "Butcher-Oemler effect" is due primarily to bursts of star formation occurring in galaxies in concentrated clusters at redshifts out to 0.5.
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Lavery et al. (1986) studied this question.