What do dynamical cluster masses really tell us about dynamics?
  The diagnostic age versus mass-to-light ratio diagram is often used in attempts to constrain the shape of the stellar initial mass function, and the stability and the potential longevity of extragalactic young to intermediate-age massive star clusters. Here, we explore the pitfalls associated with this approach and its potential for use with Galactic open clusters. We conclude that for an open cluster to survive for any significant fraction of a Hubble time (in the absence of substantial external perturbations), it is a necessary but not a sufficient condition to be located close to the predicted photometric evolutionary sequences for "normal" simple stellar populations. 
Richard de Grijs (1,2), M. B. N. Kouwenhoven (1) and Simon P. Goodwin   (1) ((1) University of Sheffield, UK; (2) NAOC-CAS, ...