The orbital motion of the Quintuplet cluster - a common origin for the Arches and Quintuplet clusters?

TL;DR

This study measures the orbital motion of the Quintuplet cluster near the Galactic center using high-resolution imaging over nearly six years, providing insights into its origin and relation to the Arches cluster.

Contribution

First measurement of the Quintuplet cluster's orbit using multi-epoch adaptive optics imaging, constraining its velocity and potential common origin with the Arches cluster.

Findings

Quintuplet's 2D velocity is 132 +/- 15 km/s along the Galactic plane.

The 3D orbital velocity of the Quintuplet is 167 +/- 15 km/s.

Velocity dispersion in the cluster core is less than 10 km/s.

Abstract

We investigate the orbital motion of the Quintuplet cluster near the Galactic center with the aim of constraining formation scenarios of young, massive star clusters in nuclear environments. Three epochs of adaptive optics high-angular resolution imaging with Keck/NIRC2 and VLT/NACO were obtained over a time baseline of 5.8 years, delivering an astrometric accuracy of 0.5-1 mas/yr. Proper motions were derived in the cluster reference frame and were used to distinguish cluster members from the majority of field stars. Fitting the cluster and field proper motion distributions with 2D gaussian models, we derive the orbital motion of the cluster for the first time. The Quintuplet is moving with a 2D velocity of 132 +/- 15 km/s with respect to the field along the Galactic plane, which yields a 3D orbital velocity of 167 +/- 15 km/s when combined with the previously known radial velocity. From a sample of 119 stars measured in three epochs, we derive an upper limit to the velocity dispersion in the core of the Quintuplet cluster of sigma_1D < 10 km/s. Knowledge of the three velocity components of the Quintuplet allows us to model the cluster orbit in the potential of the inner Galaxy. Comparing the Quintuplet's orbit with the Arches orbit, we discuss the possibility that both clusters originated in the same area of the central molecular zone. [abridged]