2D kinematics of massive stars near the Galactic Center

TL;DR

This study uses high-precision Hubble Space Telescope proper motions to analyze the 2D kinematics of massive stars near the Galactic Center, providing insights into their origins and cluster memberships.

Contribution

It offers the first detailed 2D kinematic analysis of massive stars near the GC using HST data, constraining their distances and cluster associations.

Findings

Most massive stars are within 3-4 kpc of Sgr A* based on kinematics.

Few massive stars are likely members of the Arches cluster.

No excess of high-velocity escaping stars was detected.

Abstract

The presence of massive stars (MSs) in the region close to the Galactic Center (GC) poses several questions about their origin. The harsh environment of the GC favors specific formation scenarios, each of which should imprint characteristic kinematic features on the MSs. We present a 2D kinematic analysis of MSs in a GC region surrounding Sgr A* based on high-precision proper motions obtained with the Hubble Space Telescope. Thanks to a careful data reduction, well-measured bright stars in our proper-motion catalogs have errors better than 0.5 mas yr$^{-1}$. We discuss the absolute motion of the MSs in the field and their motion relative to Sgr A*, the Arches and the Quintuplet. For the majority of the MSs, we rule out any distance further than 3-4 kpc from Sgr A* using only kinematic arguments. If their membership to the GC is confirmed, most of the isolated MSs are likely not associated with either the Arches or Quintuplet clusters or Sgr A*. Only a few MSs have proper motions suggesting they are likely members of the Arches cluster, in agreement with previous spectroscopic results. Line-of-sight radial velocities and distances are required to shed further light on the origin of most of these massive objects. We also present an analysis of other fast-moving objects in the GC region, finding no clear excess of high-velocity escaping stars. We make our astro-photometric catalogs publicly available.