The Butcher‐Oemler Effect in Abell 2317

This paper presents deep narrow band photometry of the cluster A2317(z=0.211) carried out using KPNO 4 m and Steward 2.3 m telescopes. Using restframe Stromgren photometry, it is determined that A2317 has an unusually highfraction of blue galaxies (the Butcher-Oemler effect) for its redshift(f_B=0.35). We demonstrate that the ratio of blue to red galaxies has a strongdependence on absolute magnitude such that blue galaxies dominate the top ofthe luminosity function. Spectrophotometric classification shows that amajority of the red galaxies are E/S0's, with a small number of reddenedstarburst galaxies. Butcher-Oemler galaxies are shown to be galaxies with starformation rates typical of late-type spirals and irregular. Starburst systemswere typically found to be on the lower end of the cluster luminosity function.In addition, blue galaxies are preferentially found in the outer edges of thecluster, whereas the red galaxies are concentrated in the cluster core.