Dynamical evolution of the young stars in the Galactic center

TL;DR

This paper uses N-body simulations to explore how young stars near the Galactic center evolved into their current distributions, suggesting disk evolution from gaseous origins and a capture scenario for S-stars involving three-body interactions.

Contribution

It demonstrates that the young stellar disk likely evolved from a gaseous disk and that S-stars could originate from binary captures, with scattering shaping their eccentricities.

Findings

The stellar disk could have evolved from a thin gaseous disk.

S-stars' distribution is consistent with a capture origin.

Scattering by stellar black holes influences eccentricity evolution.

Abstract

Recent observations of the Galactic center revealed a nuclear disk of young OB stars near the massive black hole (MBH), in addition to many similar outlying stars with higher eccentricities and/or high inclinations relative to the disk (some of them possibly belonging to a second disk). In addition, observations show the existence of young B stars (the 'S-cluster') in an isotropic distribution in the close vicinity of the MBH ($<0.04$ pc). We use extended N-body simulations to probe the dynamical evolution of these two populations. We show that the stellar disk could have evolved to its currently observed state from a thin disk of stars formed in a gaseous disk, and that the dominant component in its evolution is the interaction with stars in the cusp around the MBH. We also show that the currently observed distribution of the S-stars could be consistent with a capture origin through 3-body binary-MBH interactions. In this scenario the stars are captured at highly eccentric orbits, but scattering by stellar black holes could change their eccentricity distribution to be consistent with current observations.