Surface map showing the cluster velocity dispersion as a function of mass and half-mass radius. From left to right, black lines identify clusters with a velocity dispersion of 0.3, 2, 5, 10, 50, and 100 km s−1, respectively. The three black stars identify the typical values for Galactic YCs (Portegies Zwart et al. 2010), GCs (Harris 2010), and the Galactic NC (Feldmeier et al. 2014).