Galactic globular cluster 47 Tucanae: new ties between the chemical and dynamical evolution of globular clusters?

TL;DR

This study investigates the relationship between chemical compositions and kinematic behaviors of different stellar generations in the globular cluster 47 Tuc, revealing significant radial and dynamical differences linked to chemical properties.

Contribution

It provides new insights into the connection between chemical and dynamical evolution of stellar generations in 47 Tuc using detailed abundance and kinematic analysis.

Findings

First-generation stars are less centrally concentrated.

Subsequent generations are dynamically cooler.

Velocity dispersion correlates with Na and O abundances.

Abstract

It is generally accepted today that Galactic globular clusters (GGCs) consist of at least two generations of stars that are different in their chemical composition and perhaps age. However, knowledge about the kinematical properties of these stellar generations, which may provide important information for constraining evolutionary scenarios of the GGCs, is still limited. We therefore study the connections between chemical and kinematical properties of different stellar generations in the Galactic globular cluster 47 Tuc. To achieve this goal, we used abundances of Li, O, and Na determined in 101 main sequence turn-off (TO) stars with the aid of 3D hydrodynamical model atmospheres and NLTE abundance analysis methodology. We divided our sample TO stars into three groups according to their position in the [Li/Na]-[Na/O] plane to study their spatial distribution and kinematical properties. We find that there are statistically significant radial dependencies of lithium and oxygen abundances, A(Li) and A(O), as well as that of [Li/Na] abundance ratio. Our results show that first-generation stars are less centrally concentrated and dynamically hotter than stars belonging to subsequent generations. We also find a significant correlation between the velocity dispersion and O and Na abundance, and between the velocity dispersion and the [Na/O] abundance ratio.