Study of Multiple Populations in Two Dynamically Young Globular Clusters

The traditional concept of Globular Clusters (GCs) as simple stellar populations, where all stars share the same age and chemical abundances, is now outdated. It has become clear that almost all GCs host significant spreads in light-element abundances. These peculiar variations were confirmed by both spectroscopy and photometry with the discovery of Multiple Populations (MPs): a first population (FP) with a field-like composition and a second population (SP) showing anomalous chemistry unique to GCs. Dalessandro et al. (2019) demonstrated that SP stars form centrally concentrated within the clusters, whereas FP stars are more dispersed in the outer regions. This is particularly evident in dynamically young GCs, where mixing mechanisms have not yet homogenized the populations. A key issue is that only a few cases of dynamically young GCs have been studied so far. This master’s thesis aims to expand this sample by focusing on two low-density, low-mass, and dynamically young GCs: NGC 5053 and NGC 5466. Using a combination of ground-based and Hubble Space Telescope (HST) observations, we separated the two populations in each cluster and analyzed their structural properties. Surprisingly, we found that despite being dynamically young, both clusters exhibit populations that are already homogeneously mixed, in contrast with the expected scenario. Moreover, by comparing our results with other dynamically young clusters, we observed that the degree of spatial mixing correlates with cluster mass and central density: more massive and denser clusters tend to have more centrally concentrated SP stars. Further investigations are required to clarify the mechanisms driving this rapid mixing of MPs in low-density, low-mass GCs.