Dynamical state of the globular clusters Rup 106 and IC 4499

Abstract

The dynamical evolution of globular clusters is theoretically described by a series of well-known events typical of N-body systems. Still, the identification of observational signatures able to empirically describe the stage of dynamical evolution of a stellar system with a density typical of a globular cluster represents a challenge. In this paper, we study the dynamical age of the globular clusters Rup 106 and IC 4499. To this aim, we study the radial distribution of the blue straggler stars (BSSs) via the A+ parameter and of the slope of the main sequence mass function. Both tracers show that Rup 106 and IC 4499 are dynamically young clusters where dynamical friction has just started to segregate massive stars towards their respective centres. Furthermore, we observe that the BSSs are more centrally concentrated in both clusters than the reference population. Similarly, we find that in both cases the slope of the mass function significantly decreases as a function of the cluster-centric distance. This result provides additional support for the use of the radial distribution of the BSSs as a powerful and observationally convenient indicator of the cluster dynamical age.