The angular momentum of stars reflects the relationship between star-forming environment and galactic evolution history

TL;DR

This paper investigates how stellar angular momentum reflects the history of star-forming environments in the Milky Way, revealing an inverse relationship with age that informs galactic evolution and star formation processes.

Contribution

It demonstrates that stellar angular momentum correlates with age, indicating changes in star-forming environments over galactic history, and links angular momentum trends to initial mass function variations.

Findings

Stars with 1.4-1.8 M_sun show inverse angular momentum-age relation.

Angular momentum conservation validates measurement reliability.

Evolved stars tend to have higher rotational angular momenta.

Abstract

This study focuses on stars with masses above the Kraft break in the \textit{Kepler} field. Their rotational angular momenta are essentially the same as those at the zero-age main sequence. The angular momentum dissipation experienced by these stars during their pre-main sequence phase is also relatively weak, so their rotational angular momentum can reflect the parameters of their parental molecular clouds. The reliability of angular momentum measurements was evaluated based on the phenomenon of angular momentum conservation observed in stars before and after the turn-off point in observational data. We find that stars with masses between 1.4$M_\odot$ and 1.8$M_\odot$ show an inverse proportionality between angular momentum and isochrone age. We propose that the angular momentum-age correlation reflects changes in the star-forming environment in the Milky Way's history. Besides, the observed inverse proportionality implies that, as the Milky Way has evolved, the stars formed within it tend to possess greater rotational angular momenta. This trend would promote the fragmentation of stars during the pre-main sequence phase and inhibit the formation of massive stars, providing a useful perspective for explaining variations in the initial mass function.