The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic structure

TL;DR

This study investigates the kinematic structure of the IRS 13 stellar cluster near Sgr A*, revealing a disk-like formation, evidence of cluster migration, and potential signs of an intermediate-mass black hole, advancing understanding of Galactic Center dynamics.

Contribution

The paper uncovers a new disk-like structure in IRS 13, demonstrates possible cluster migration via simulations, and suggests the presence of an intermediate-mass black hole based on spectral analysis.

Findings

Evidence for a disk-like stellar structure in IRS 13.

Simulation results support cluster migration towards the inner parsec.

Spectral data suggest an intermediate-mass black hole of ~3 x 10^26 M_sun.

Abstract

The existence of two distinct and apparently unrelated populations of dusty stellar objects in the Nuclear Stellar Cluster (NSC) of the Milky Way, namely IRS 13 and the S-cluster, are potentially prone to a general process describing the star formation history in the Galactic Center (GC). The former cluster is thought to be entangled in the clockwise and counterclockwise disks, a large-scale stellar distribution revealed by the analysis of stars at different distances from Sgr A*, the supermassive black hole in the GC. Recently, this large-scale distribution was reported to exhibit a multi-disk structure with at least four components. Motivated by this finding, we revisit the anisotropic IRS 13 cluster and find strong evidence for a disk-like structure. An examination of about 50 individual stellar orbits reveals a new structure that does not follow any trend known in the literature. Furthermore, we investigate the possibility of an inspiral cluster undergoing star formation processes, as proposed by several authors. Using a simplified N-body simulation to reproduce our observational results, we conclude that, under certain conditions, a massive cluster can migrate from the Circum Nuclear Disk toward the inner parsec. Based on this classification, we revisit the large-scale NACO (VLT) observations of IRS 13 and find evidence for a separation of the cluster into a gravitationally stable core remnant and a dissipating part. With the velocity-resolved H30{\alpha} line and the broadband spectral energy distribution of IRS 13E3, we provide tentative support for the existence of an intermediate-mass black hole of ~ 3 x 10^26 M_sun surrounded by a hot gaseous stream.