Observing dynamical friction in galaxy clusters
  We present a novel method to detect the effects of dynamical friction in observed galaxy clusters. Following accretion into clusters, massive satellite galaxies will backsplash to systematically smaller radii than less massive satellites, an effect that may be detected by stacking the number density profiles of galaxies around clusters. We show that this effect may be understood using a simple toy model which reproduces the trends with halo properties observed in simulations. We search for this effect using SDSS redMaPPer clusters with richness 10<lambda<20, and find that bright (M_i<-21.5) satellites have smaller splashback radii than fainter (M_i>-20) satellites at 99% confidence. 
Susmita Adhikari, Neal Dalal, Joseph Clampitt
astro-ph.CO astro-ph.GA