Revealing Multiple Populations in Omega Centauri Through Data-Driven Hierarchical Clustring (No. 169)
European Astronomical Society Annual Meeting 2026, Lausanne, İsviçre, 29 Haziran - 03 Temmuz 2026, ss.1-5, (Tam Metin Bildiri)
- Yayın Türü: Bildiri / Tam Metin Bildiri
- Basıldığı Şehir: Lausanne
- Basıldığı Ülke: İsviçre
- Sayfa Sayıları: ss.1-5
- Akdeniz Üniversitesi Adresli: Evet
Özet
Omega Centauri (NGC 5139) is the largest and chemically most complex globular cluster in the Milky Way and is widely regarded as a fundamental benchmark system for the study of multiple stellar populations. Its broad metallicity distribution and well-known elemental abundance variations make it an ideal laboratory for disentangling stellar populations through data-driven methods.
In this study, we aimed to identify and characterize the multiple stellar populations of Omega Centauri within a fully data-driven framework using hierarchical clustering in chemical abundance space. We defined population boundaries by employing elemental abundances that are known in the literature to be discriminative for sub-population separation in globular clusters. These elements include iron-peak and light elements that trace the nucleosynthetic processes of Type II and Type Ia supernovae, as well as asymptotic giant branch (AGB) stars.
As a result of the hierarchical clustering analysis applied in multidimensional chemical space, we identified ten statistically distinct sub-populations. The clustering structure naturally emerged from the correlations among elemental abundances, without imposing prior assumptions about the number or properties of the populations. For each identified sub-population, we computed the median values and dispersions of additional chemical abundances beyond the primary clustering parameters. The results show that each sub-population exhibits systematically different median abundance patterns; this confirms that the clustering outcome reflects genuine chemical differentiation rather than statistical noise.
To place these chemically defined groups into an evolutionary context, we determined their ages using Gaia two-color diagrams combined with a Markov Chain Monte Carlo (MCMC)-based isochrone fitting method. For each sub-population, theoretical isochrones were fitted to the corresponding photometric sequences within a probabilistic framework to derive age estimates. This approach enables reliable uncertainty estimation and reduces biases associated with manual sequence selection.
The resulting age distributions reveal systematic differences among the chemically separated groups and indicate a complex and extended star formation history within Omega Centauri. The joint evaluation of chemical clustering and independent age determination has enabled a coherent reconstruction of the cluster’s evolutionary timeline. Our findings support a scenario in which Omega Centauri experienced multiple enrichment episodes, each leaving a distinct chemical signature and age distribution.
One of the main contributions of this study is demonstrating that hierarchical clustering in chemical space, when combined with probabilistic age modeling, can recover physically meaningful stellar populations without relying on predefined chromosome maps or Gaussian mixture models. It is shown that the multidimensional abundance structure alone contains sufficient information to distinguish different stellar generations in chemically complex systems.
Beyond Omega Centauri, this study serves as a methodological reference for testing the applicability of similar data-driven techniques to other globular and open clusters hosting multiple populations. The successful implementation of the method in the chemically most complex cluster provides a scalable and reproducible framework that can be extended to large-scale spectroscopic survey data.
In conclusion, this study identifies ten chemically distinct sub-populations in Omega Centauri through a fully data-driven approach, demonstrates their internal chemical coherence, and constrains their relative ages via MCMC-based isochrone fitting. The results offer a new perspective on the formation and chemical enrichment history of this unique system and establish a solid methodological foundation for future studies of multiple populations in star clusters.