Tides, interactions, and fine-scale substructures in galaxy clusters

We present the results of a study on galaxy interactions, tides, and other processes that produce luminous fine-scale substructures in the galaxy clus ters: Coma, Perseus, Abell 2199, AWM 3, and AWM 5. All unusual structures i n these clusters can be categorized into seven morphologies: interacting ga laxies, multiple galaxies (noninteracting), distorted galaxies, tailed gala xies, line galaxies, dwarf galaxy groups, and galaxy aggregates. The variou s morphologies are described, and a catalog is presented, of 248 objects in these five clusters along with color, and positional information obtained from CCD images taken with the WIYN 3.5 m telescope in broadband B and R fi lters. Distorted, interacting, and fine-scale substructures have a range of colors extending from blue objects with B-R approximate to O to redder colors at B-R approximate to 2.5. We also find that the structures with the most dist urbed morphology have the bluest colors. In addition, the relative number d istributions of these structures suggest that two separate classes of galax y clusters exist: one dominated by distorted structures and the other domin ated by galaxy associations. The Coma and Perseus clusters, respectively, a re proposed as models for these types of clusters. These structures avoid t he deep potentials of the dominant D or cD galaxies in the Coma and Perseus clusters, and tend to clump together. Possible mechanisms for the production of fine-scale substructure are revie wed and compared with observations of z approximate to 0.4 Butcher-Oemler c lusters. We conclude, based on color, positional, and statistical data, tha t the most likely mechanism for the creation of these structures is through an interaction with the gravitational potential of the cluster, possibly c oupled with effects of weak interactions with cluster ellipticals.