2000ApJ...540..715R

This paper presents four-color narrowband photometry of clusters A115 (z=0.191) and A2283 (z=0.182) in order to follow the star formation history of various galaxy types. Although located at similar redshifts, the two clusters display very different fractions of blue galaxies (i.e., the Butcher-Oemler effect; f_B=0.13 for A115, f_B=0.30 for A2283). A system of photometric classification is applied to the cluster members that divides the cluster population into four classes based on their recent levels of star formation. It is shown that the blue population of each cluster is primarily composed of normal star-forming (star formation rate<1 M_☉.yr^–1) galaxies at the high-luminosity end but with an increasing contribution from a dwarf starburst population below M₅₅₀₀=-20. This dwarf starburst population appears to be the same population of low-mass galaxies identified in recent Hubble Space Telescope imaging, possible progenitors to present-day cluster dwarf ellipticals, irregulars, and blue compact dwarfs. Deviations in the color-magnitude relationship for the red galaxies in each cluster suggest that a population of blue S0s is evolving into present-day S0 colors at this epoch. The radial distribution of the blue population supports the prediction of galaxy harassment mechanisms for tidally induced star formation operating on an infalling set of gas-rich galaxies.