Associations of Dwarf Galaxies

Hubble Space Telescope Advanced Cameras for Surveys has been used todetermine accurate distances for 20 galaxies from measurements of theluminosity of the brightest red giant branch stars. Five associations of dwarfgalaxies that had originally been identified based on strong correlations onthe plane of the sky and in velocity are shown to be equally well correlated indistance. Two more associations with similar properties have been discovered.Another association is identified that is suggested to be unbound through tidaldisruption. The associations have the spatial and kinematic properties expectedof bound structures with 1 - 10 x 10^11 solar mass. However, these entitieshave little light with the consequence that mass-to-light ratios are in therange 100 - 1000 in solar units. Within a well surveyed volume extending to 3Mpc, all but one known galaxy lies within one of the groups or associationsthat have been identified.Comment: 50 pages, 2 tables, 15 encapsulated figures, 1 (3 part) jpg figure. Submitted to Astronomical Journa