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K. Chiboucas, M. Mateo (University of Michigan)
The galaxy luminosity function (LF) is a fundamental tool for understanding galaxy evolution and faint galaxy populations. The shape of the cluster LF provides information on the initial formation and subsequent evolution of galaxies in clusters while the power law slope at the faint-end indicates how steeply the dwarf number counts rise as a function of magnitude and, assuming a mass to light ratio such as has been found for Local Group dwarfs, how much mass the dwarfs may contribute to the total mass of the universe. Much work has been done on the cluster LF, with various groups finding differences in its shape and the faint-end slope (with values ranging from -1.3 to -2.3) for different clusters. While cluster environmental effects may be the cause of this range, it may also be a consequence of the different detection techniques and treatments of the selection effects inherent in detecting these low luminosity, low surface brightness systems. We are investigating the cluster-to-cluster variations in the LF and dwarf galaxy properties in order to isolate specific physical effects that modify dwarf properties and govern dwarf evolution in clusters. We present our methods and results from our first cluster, Centaurus, which serves as an example of our techniques. Deep V-band images covering large areas of 9 nearby (z < 0.03) galaxy clusters have been obtained and we are carefully dealing with the selection effects by using false galaxy tests. Because we are employing the same method and analysis for every cluster in our data set, results from each cluster will be directly comparable enabling us to establish whether intrinsic variations in the LF do exist between clusters. In order to determine specific cluster environmental effects which could modify the shape and faint-end slope of the LF we further examine dwarf properties as a function of cluster location and environment and global dwarf-to-giant ratios.