Chemical tagging of tidal tail star candidates of NGC 6362

TL;DR

This study used spectroscopic analysis to investigate the chemical composition of tidal tail star candidates of NGC 6362, revealing they are mostly Milky Way disk stars rather than cluster members, challenging previous assumptions about their origins.

Contribution

It provides the first detailed chemical abundance analysis of tidal tail candidates of NGC 6362, showing they are not chemically similar to the cluster and are likely Milky Way disk stars.

Findings

Tidal tail candidates do not share the cluster's metallicities or element abundances.

Radial velocity distributions differ from those of the cluster, indicating non-membership.

Most candidates are similar to Milky Way thick disk stars.

Abstract

The inner Milky Way disk globular cluster NGC~6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color-magnitude diagram similar to those of cluster stars. Because recent results seem also to show that these stars are distributed across the regions least affected by interstellar absorption and reproduce the observed composite star field density map, we carried out a detailed spectroscopic analysis of a number of chemical element abundances of tidal tail star candidates in order to investigate the relationship of them with NGC~6362. From European Southern Observatory's VLT@FLAMES spectra we found that the red giant branch stars selected as cluster's tidal tail stars do not have overall metallicities nor abundances of Mg, Ca, Sc, Ti, Cr, Ni and Ba similar to the cluster's ones. Moreover, they are mainly alike to stars that belong to the Milky Way thick disk, some of them could be part of the thin disk and a minor percentage could belong to the Milky Way halo star population. On the other hand, since the resulting radial velocities do not exhibit a distribution function similar to that of cluster's stars, we concluded that looking for kinematic properties similar to those of the cluster would not seem to be an approach for selecting cluster's tidal tail stars as suitable as previously thought.