Omega Centauri stands as a unique anomaly among Globular Clusters (GCs) in the Milky Way, with an extreme mass and chemical complexity widely considered the relic nucleus of an accreted dwarf galaxy. However, the full extent of its progenitor’s debris has remained a subject of intense debate. In this presentation, I will present our hypothesis of a unified progenitor : the Omega Dwarf. Utilising high-resolution spectroscopic abundances from the APOGEE and GALAH surveys and combining with Gaia DR3 astrometry, we reconstruct the multi-dimensional chemical space of the Omega Dwarf stellar populations and perform chemical stratigraphy across the disrupted dwarf galaxy. Our findings reveal a clear spatial-chemical segregation : chemically evolved populations, characterised by enrichments in aluminium, nitrogen, and helium, are tightly confined to the deepest potential wells, suggesting a secondary, high-density star-formation burst during the merger. The metallicity profile exhibits an inverted U-shape, a hallmark of present-day nucleated dwarf galaxies where central gas inflows drive late-stage enrichment. Furthermore, the inner region shows a marked alpha-enhancement compared to the outskirts, indicating a shorter, more efficient star-formation timescale likely fuelled by the rapid migration of inspiralling GCs. Ultimately, our results support a scenario in which the Omega Dwarf was a major contributor to the assembly of the Milky Way’s stellar halo, with Omega Centauri as its final, resilient survivor.
The Omega Dwarf : Chemical Stratigraphy of the Disrupted Dwarf Galaxy That Left Behind Omega Centauri
Lundi 22 juin 2026
de
14:00 à
15:00
Conference room, building 17
