The origin of S-stars and a young stellar disk: distribution of debris stars of a sinking star cluster

TL;DR

This study uses N-body simulations to propose that a young star cluster with an intermediate-mass black hole can explain the formation and distribution of both disk and S-star populations near the Galactic center.

Contribution

It introduces a self-consistent dynamical model showing how a star cluster with an IMBH can produce the observed stellar distributions and properties near the GC.

Findings

Stars carried by the IMBH are distributed with a top-heavy mass function within 10".

Surface density of young stars follows a slope of -1.5 within 10".

The central stellar distribution is isotropic, matching observations.

Abstract

Within the distance of 1 pc from the Galactic center (GC), more than 100 young massive stars have been found. The massive stars at 0.1-1 pc from the GC are located in one or two disks, while those within 0.1 pc from the GC, S-stars, have an isotropic distribution. How these stars are formed is not well understood, especially for S-stars. Here we propose that a young star cluster with an intermediate-mass black hole (IMBH) can form both the disks and S-stars. We performed a fully self-consistent $N$-body simulation of a star cluster near the GC. Stars escaped from the tidally disrupted star cluster were carried to the GC due to an 1:1 mean motion resonance with the IMBH formed in the cluster. In the final phase of the evolution, the eccentricity of the IMBH becomes very high. In this phase, stars carried by the 1:1 resonance with the IMBH were dropped from the resonance and their orbits are randomized by a chaotic Kozai mechanism. The mass function of these carried stars is extremely top-heavy within 10". The surface density distributions of young massive stars has a slope of -1.5 within 10" from the GC. The distribution of stars in the most central region is isotropic. These characteristics agree well with those of stars observed within 10" from the GC.