Open clusters in 2MASS photometry II. Mass Function and Mass Segregation
  This is a continuation of our study of open clusters based on the 2--Micron All Sky Survey photometry. Here we present the results of the mass function analysis for 599 known open clusters in the Milky Way. The main goal of this project is a study of the dynamical state of open clusters, the mass segregation effect and an estimate of the total mass and the number of cluster members. We noticed that the cluster size (core and overall radii) decreases along dynamical evolution of clusters. The cluster cores evolve faster than the halo regions and contain proportionally less low-mass stars from the beginning of the cluster dynamical evolution. We also noticed, that the star density decreases for the larger clusters. Finally, we found an empirical relation describing the exponential decrease of the mass function slope with the dynamical evolution of clusters. 
L. Bukowiecki, G. Maciejewski, P. Konorski, A. Niedzielski
astro-ph.SR astro-ph.GA