The role of rotation on the formation of second generation stars in globular clusters

TL;DR

This study uses 3D hydrodynamic simulations to investigate how rotation influences the formation and properties of second-generation stars in globular clusters, revealing complex chemo-dynamical patterns.

Contribution

It introduces detailed simulations of rotating globular clusters forming second-generation stars from AGB ejecta and external gas, highlighting the impact of rotation and gas density on stellar dynamics.

Findings

SG stars form a rotating disk with helium enhancement.

Higher external gas density disrupts the SG disk formation.

Rotation patterns depend on initial conditions and gas infall parameters.

Abstract

By means of 3D hydrodynamic simulations, we explore the effects of rotation in the formation of second-generation (SG) stars in globular clusters (GC). Our simulations follow the SG formation in a first-generation (FG) internally rotating GC; SG stars form out of FG asymptotic giant branch (AGB) ejecta and external pristine gas accreted by the system. We have explored two different initial rotational velocity profiles for the FG cluster and two different inclinations of the rotational axis with respect to the direction of motion of the external infalling gas, whose density has also been varied. For a low (10^-24 g cm^-3) external gas density, a disk of SG helium-enhanced stars is formed. The SG is characterized by distinct chemo-dynamical phase space patterns: it shows a more rapid rotation than the FG with the helium-enhanced SG subsystem rotating more rapidly than the moderate helium-enhanced one. In models with high external gas density (10^-23 g cm^-3), the inner SG disc is disrupted by the early arrival of external gas and only a small fraction of highly enhanced helium stars preserves the rotation acquired at birth. Variations in the inclination angle between the rotation axis and the direction of the infalling gas and the velocity profile can slightly alter the extent of the stellar disc and the rotational amplitude. No significant variation has been found in the timespan of our simulations when changing the inclination angle between the rotation axis and the direction of the infalling gas, while different velocity profiles can slightly alter the extent of the stellar disc and the rotational amplitude. The results of our simulations illustrate the complex link between dynamical and chemical properties of multiple populations and provide new elements for the interpretation of observational studies and future investigations of the dynamics of multiple-population GCs.