Cosmic-Lab: Understanding the Dynamical Evolution of Dense Stellar Systems

In this Thesis, I study the dynamics of blue straggler stars (BSSs) in globular clusters (GCs) by means of direct N-body simulations. Due to their mass larger than the average star mass in GCs, BSSs suffer for dynamical friction (DF), which causes their sinking and segregation toward the cluster centre. Observationally, the BSS normalized radial distribution (BSS-nRD) has been found to show three different shapes, which have been interpreted as due to different dynamical ages of the host clusters (Ferraro et al. 2012, Nature, 492, 393). The proposed scenario is that, as a GC get dynamically older, BSSs progressively segregate in its centre (thus producing a central peak in the BSS-nRD), while a minimum in the distribution appears at progressively larger distances from the centre, marking the (dynamical) time flow, just as the hand of a "dynamical clock" (thus defining the dynamical-clock scenario). The aim of this Thesis is to search for these observed features in direct N-body simulations, and to provide realistic models able to describe all the processes that contribute in shaping the BSS-nRD. I performed different sets of N-body simulations, including a population of dark remnants, such as neutron stars (NSs) and stellar mass black holes (BHs), which have been revealed to significantly inhibit the segregation of BSSs. Moreover, I defined a new mass segregation indicator, which is found to be a powerful observational tool able to replace the previous dynamical-clock indicator.