Chemo-dynamical complexity of omega Centauri

We measure both global kinematic quantities and radial profiles for each chemically defined group, extending from the inner regions to ~4 half-light radii. The Gaussian Mixture Model identifies five chemical components, which, when examined through their radial cumulative distributions, naturally group into two broader families characterised by lower and higher aluminium enrichment. The two families differ significantly in their spatial and kinematic properties: the Al-rich stars are more centrally concentrated and exhibit stronger radial anisotropy than the Al-poor stars, which remain closer to isotropy over the radial range probed.

Despite these significant differences (>2{sigma}), the two populations share a common rotation pattern, with comparable intrinsic rotation amplitudes and rotation-axis inclinations within the uncertainties (~0.5km/s). Both families span a wide range in metallicity, indicating that they do not simply correspond to a first- and second-generation dichotomy, but rather trace chemically and dynamically complex substructures within omega Cen.

This work represents the first chemo-dynamical study of omega Cen linking detailed chemical tagging to internal kinematics from the inner regions to the cluster outskirts, and provides a key benchmark for models of its formation. A formation path involving both hierarchical assembly within a dwarf-galaxy potential and centrally concentrated, chemically enriched star formation offers a natural explanation for the observed chemo-dynamical complexity.

Extending this approach to larger fields of view and to more numerous, fainter stars will be essential to robustly uncover the origin of this uniquely complex system.