2019MNRAS.488..253S

We report the first radial velocity measurements of the recently identified globular cluster FSR1758. From the two member stars with radial velocities from the Gaia Radial Velocity Spectrograph reported in Gaia DR2, we find FSR1758 has a radial velocity of 227 ± 1 \textrmkm \textrms^–1. We also find potential extra-tidal star lost from the cluster in the surrounding 1 deg. Combined with Gaia proper motions and photometric distance estimates, this shows that FSR1758 is on a relatively retrograde, radial orbit with a pericentre of 3.8_–0.9^+0.9 kpc, an apocentre of 16_–5⁺⁸ kpc, and eccentricity of 0.62_–0.04^+0.05. Although it is currently at a Galactocentric distance of 3.8_–0.9^+0.9 kpc - at the edge of the bulge - it is an intruder from the halo. We investigate whether a reported 'halo' of stars around FSR1758 is related to the cluster, and find that most of these stars are likely foreground dwarf stars. We conclude that FSR1758 is not a dwarf galaxy, but rather a globular cluster.