Neighbors, not kin: Kinematic evidence of tidal tails from NGC 7492 along the Sagittarius stream

Context . The formation, extension, and morphology of extra-tidal stars around globular clusters depend on the internal kinematics of the host cluster and the influence of the Galactic potential. Tracing the kinematics of faint tidal tails sheds light on their formation and contribution to the Milky Way halo assembly. Aims . NGC 7492 is an outer halo globular cluster with conflicting evidence regarding the presence of tidal tails. If present, the tails are expected to be faint and embedded in the Sagittarius tidal stream, located at a similar heliocentric distance but having different kinematics. Methods . We carried out a GIRAFFE/FLAMES spectroscopic follow-up of ten fields at the expected location of tidal tails associated with NGC 7492 to obtain the radial velocity component. Gaia parallaxes were used to remove foreground contaminants, while only loose constraints on Gaia proper motion were applied to select the targets. From the high-resolution spectra, radial velocities and metallicities were derived for more than 700 stars, from the red giant branch down to the upper main sequence. Results . Cluster and extra-tidal stars were identified based on their proper motions, radial velocities, and metallicities. This population extends over at least ∼1.8 deg from the cluster center, confirming the tidal tails previously detected only photometrically. The extra-tidal stars are located at positions consistent with spray-particle models for the cluster’s disruption. The Sagittarius stream is also clearly identified through its distinct proper motion distribution, radial velocities and more metal-rich population. Conclusions . Despite the low spatial density of extra-tidal stars, the kinematic signature of the cluster is clearly detected, confirming the presence of tidal tails overlapping on the sky with the Sagittarius stream, although the two structures are physically unrelated. The present spectroscopic dataset provides a robust basis for future studies aimed at extending the characterization of the tails, both in extension and limiting magnitude.