Rotation and multiple stellar population in globular clusters

TL;DR

This study uses 3D hydrodynamical simulations to explore how second-generation stars in globular clusters form with significant rotation, potentially influencing the clusters' current shapes and internal dynamics.

Contribution

It demonstrates that second-generation stars formed from AGB ejecta can have substantial initial rotation, affecting the long-term structure and kinematics of globular clusters.

Findings

SG can have V/sigma ~0.8-2.5, indicating significant rotation.

Initial kinematics of FG strongly influence SG rotation.

Long-term evolution can preserve initial rotational features.

Abstract

We investigate structure and kinematics of the second generation of stars (SG) formed from gaseous ejecta of the first generation of stars (FG) in forming globular clusters (GCs). We consider that SG can be formed from gaseous ejecta from AGB stars of FG with the initial total mass of 10^6-10^8 M_sun to explain the present masses of the Galactic GCs. Our 3D hydrodynamical simulations with star formation show that SG formed in the central regions of FG can have a significant amount of rotation (V/sigma ~0.8-2.5). The rotational amplitude of SG can depend strongly on the initial kinematics of FG. We thus propose that some GCs composed of FG and SG had a significant amount of rotation when they were formed. We also suggest that although later long-term (~10 Gyr) dynamical evolution of stars can smooth out the initial structural and kinematical differences between FG and SG to a large extent, initial flattened structures and rotational kinematics of SG can be imprinted on shapes and internal rotation of the present GCs. We discuss these results in terms of internal rotation observed in the Galactic GCs.