THE BUTCHER-OEMLER EFFECT IN ABELL-2317

This paper presents deep narrowband photometry of the cluster A2317 (z = 0.211) carried out using the KPNO 4 m and Steward 2.3 m telescopes. Using rest frame Stromgren photometry, it is determined that A2317 ha s an unusually high fraction of blue galaxies (the Butcher-Oemler effe ct) for its redshift (f(B) = 0.35). We demonstrate that the ratio of b lue to red galaxies has a strong dependence on absolute magnitude such that blue galaxies dominate the top of the luminosity function. Spect rophotometric classification shows that a majority of the red galaxies are E/SO's, with a small number of reddened starburst galaxies. Butch er-Oemler galaxies are shown to be galaxies with star formation rates typical of late-type spirals and to be irregular. Starburst systems we re typically found to be on the lower end of the cluster luminosity fu nction. In addition, blue galaxies are preferentially found in the out er edges of the cluster, whereas the red galaxies are concentrated in the cluster core.