Ratio between the mean radial velocity and the radial velocity dispersion for clusters younger than 300 Myr (according to Cantat-Gaudin et al. 2020). Errors on the y-axes were obtained directly from the MCMC samples, and ages are from Cantat-Gaudin et al. (2020). In the left panel, clusters are color-coded according to the number of members. The standard deviation (and twice the value) of the ⟨v_R⟩/σ_R ratio obtained from numerical realizations of equilibrium star clusters (see Sect. 4.2) are shown as gray-shaded areas. Values obtained from numerical realizations were convolved with the median observational error to allow for a direct comparison with the underlying data. In the middle panel, colors depict R₅₀, whereas in the right panel, the color coding represents the ratio between the slope and the corresponding error from the linear regression of radial velocities as a function of cluster-centric distance.