The Interaction between Stars and Past AGN Disk: Possible Explanation for the Kinematic Distributions of S-stars in the Galactic Center

Abstract

The presence of young stars, aged around several million years and situated within the range of ∼0.04–1 pc from our Galactic center raises a question about their origins and dynamical evolutions. Their kinematics provide an opportunity to explore their formation or possible subsequent dynamical evolution. If Sagittarius A* was active in the past as suggested by several observations, the accretion disk may have a significant impact on the dynamics of stars in the Galactic center. The drag force exerted on stars during star–disk interaction could lead some of them to sink into the accretion disk, and these embedded stars will rapidly migrate inward and eventually be disrupted within ∼10 ^5 yr. This could roughly explain the absence of stars within 2.5 × 10 ^4 R _g (∼1000 au). Additionally, Kozai–Lidov oscillations, induced by the gravitational perturbation of the disk, could contribute to the bimodal distribution of S-star inclinations and drive a majority of stars into high-eccentricity orbits.

Keywords

• Active galactic nuclei
• Galactic center
• Stellar dynamics