Variation of the cluster luminosity function across the disk of M51
  We study the luminosity function (LF) of the star clusters in M51. Comparing the observed LF with the LF resulting from artificial cluster populations suggests that there exists an upper mass limit for clusters and that this limit and/or the cluster disruption varies with galactocentric distance. 
M.R. Haas, M. Gieles, R.A. Scheepmaker, S.S. Larsen, H.J.G.L.M.   Lamers, N. Bastian