The Formation of Low-Mass Cluster Galaxies and the Universal Initial Galaxy Mass Function

Clusters of galaxies have an observed over-density of low-luminosity systemsin comparison to the field, although it is not yet agreed whether this effectis the result of initial galaxy mass functions that vary with environment orgalaxy evolutionary effects. In this letter we argue that this over-density isthe result of low-mass systems with red colors that are over-populating thefaint-end of the observed luminosity function in the nearby rich cluster Abell0426. We show that the luminosity function of Abell 0426 becomes steeper, fromthe field value alpha = -1.25+/-0.05 to alpha=-1.44+/-0.04, due to a recentlyidentified population of red low-mass cluster galaxies that are possibly theremnants of dynamical stripped high-mass systems. We further demonstrate,through simple models of stripping effects, how cluster luminosity functionscan become artificially steep over time from the production of these low-masscluster galaxies.Comment: Accepted to ApJ letter