The Tale of the Milky Way Globular Cluster NGC 6362 -- I. The Orbit and its possible extended star debris features as revealed by Gaia DR2

TL;DR

This study uses Gaia DR2 data to identify potential extended star debris around NGC 6362, traces its orbit in the Milky Way, and analyzes the effects of Galactic dynamics on the cluster and its debris.

Contribution

It provides the first detailed analysis of NGC 6362's orbit and possible extended debris features, linking them to Galactic shocks and bar influence.

Findings

Identified 259 candidate debris objects around NGC 6362.

Orbit analysis shows the cluster's inner disk-like orbit and recent disk-shocking events.

Debris likely results from Galactic shocks and cluster evaporation.

Abstract

We report the identification of possible extended star debris candidates beyond the cluster tidal radius of NGC 6362 based on the second {\it Gaia} data release ({\it Gaia} DR2). We found 259 objects possibly associated with the cluster lying in the vicinity of the giant branch and 1--2 magnitudes fainter/brighter than the main-sequence turn-off in the cluster color-magnitude diagram and which cover an area on the sky of $\sim$4.1 deg$^{2}$ centered on the cluster. We traced back the orbit of NGC 6362 in a realistic Milky-Way potential, using the \texttt{GravPot16} package, for 3 Gyrs. The orbit shows that the cluster shares similar orbital properties as the inner disk, having peri-/apo-galactic distances, and maximum vertical excursion from the Galactic plane inside the corotation radius (CR), moving inwards from CR radius to visit the inner regions of the Milky Way. The dynamical history of the cluster reveals that it has crossed the Galactic disk several times in its lifetime and has recently undergone a gravitational shock, $\sim 15.9$ Myr ago, suggesting that less than 0.1\% of its mass has been lost during the current disk-shocking event. Based on the cluster's orbit and position in the Galaxy, we conclude that the possible extended star debris candidates are a combined effect of the shocks from the Galactic disk and evaporation from the cluster. Lastly, the evolution of the vertical component of the angular momentum shows that the cluster is strongly affected dynamically by the Galactic bar potential.