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The innermost regions of most galaxies are characterised by the presence ofextremely dense nuclear star clusters. Nevertheless, these clusters are not theonly stellar component present in galactic nuclei, where larger stellarstructures known as nuclear stellar discs, have also been found. Understandingthe relation between nuclear star clusters and nuclear stellar discs ischallenging due to the large distance towards other galaxies which limits theiranalysis to integrated light. The Milky Way's centre, at only 8 kpc, hosts anuclear star cluster and a nuclear stellar disc, constituting a unique templateto understand their relation and formation scenario. We aim to study thekinematics and stellar metallicity of stars from the Milky Way's nuclear starcluster and disc to shed light on the relation between these two Galacticcentre components. We used publicly available photometric, proper motions, andspectroscopic catalogues to analyse a region of $\sim2.8'\times4.9'$ centred onthe Milky Way's nuclear star cluster. We built colour magnitude diagrams, andapplied colour cuts to analyse the kinematic and metallicity distributions ofMilky Way's nuclear star cluster and disc stars with different extinction alongthe line of sight. We detect kinematics and metallicity gradients for theanalysed stars along the line of sight towards the Milky Way's nuclear starcluster, suggesting a smooth transition between the nuclear stellar disc andcluster. We also find a bi-modal metallicity distribution for all the analysedcolour bins, which is compatible with previous work on the bulk population ofthe nuclear stellar disc and cluster. Our results suggest that these twoGalactic centre components might be part of the same structure with the MilkyWay's nuclear stellar disc being the grown edge of the nuclear star cluster.

Smooth kinematic and metallicity gradients reveal that the Milky Way's nuclear star cluster and disc might be part of the same structure