Studying stellar populations in Omega Centauri with phylogenetics

P. Jofré; C. Aguilera-Gómez; P. Villarreal; F. A. Cubillos; P. Das; X. Hua; R. Yates; P. Silva; S. Vitali; T. Peña; T. Signor; K. Walsen; P. Tissera; A. Rojas-Arriagada; E. Johnston; G. Gilmore; R. Foley

doi:10.1051/0004-6361/202554863

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Volume 699 (July 2025)

A&A, 699 (2025) A291

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Issue		A&A Volume 699, July 2025


Article Number		A291
Number of page(s)		22
Section		Galactic structure, stellar clusters and populations
DOI		https://doi.org/10.1051/0004-6361/202554863
Published online		17 July 2025

A&A, 699, A291 (2025)

Studying stellar populations in Omega Centauri with phylogenetics

P. Jofré¹^,2^★, C. Aguilera-Gómez²^,3, P. Villarreal⁴^,5^,6, F. A. Cubillos⁴^,5, P. Das⁷, X. Hua⁸, R. Yates⁹, P. Silva²^,3, S. Vitali¹, T. Peña⁴^,5, T. Signor¹^,10, K. Walsen¹^,2^,11, P. Tissera²^,3^,12, A. Rojas-Arriagada²^,13^,14^,15, E. Johnston¹^,2, G. Gilmore¹⁶^,17 and R. Foley¹⁸

¹ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Ejército Libertador 441, Santiago, Chile
² Millennium Nucleus ERIS, Chile
³ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
⁴ Millennium Institute for Integrative Biology (iBio), Santiago, Chile
⁵ Centro de Genómica y Bioinformática, Facultad de Ciencias, Ingeniería y Tecnología, Universidad Mayor, Santiago, Chile
⁶ Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de, Chile
⁷ School of Mathematics and Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK
⁸ Mathematical Sciences Institute, Australian National University, Canberra ACT 2601, Australia
⁹ Centre for Astrophysics Research, University of Hertfordshire, Hatfield, AL10 9AB, UK
¹⁰ Inria Chile Research Center, Av. Apoquindo 2827, piso 12, Las Condes, Santiago, Chile
¹¹ Departamento de Ingeniería Matemática, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Beauchef 851, 8370458 Santiago, Chile
¹² Centro de Astroingeniería, Pontificia Universidad Católica de Santiago, Av. Vicuña Makenna 4860, Santiago, Chile
¹³ Departamento de Física, Universidad de Santiago de Chile, Av. Victor Jara 3659, Santiago, Chile
¹⁴ Millenium Institute of Astrophysics (MAS), Av. Vicuña Mackenna 4860, 82-0436 Macul, Santiago, Chile
¹⁵ Center for Interdisciplinary Research in Astrophysics and Space Exploration (CIRAS), Universidad de Santiago de Chile, Santiago, Chile
¹⁶ Institute of Astronomy, University of Cambridge, Madingley Road, CB3 OHA, Cambridge, UK
¹⁷ Institute of Astrophysics, FORTH Cert, N. Plastira 100, GR-70013 Vassilika Vouton, Crete, Greece
¹⁸ Leverhulme Centre for Human Evolutionary Studies, Department of Archaeology, University of Cambridge, Fitzwilliam Street, Cambridge CB2 1QH, UK

^★ Corresponding author: paula.jofre@mail.udp.cl

Received: 29 March 2025
Accepted: 2 June 2025

Abstract

Context. The nature and formation history of our Galaxy’s largest and most enigmatic stellar cluster, known as Omega Centauri (ω Cen) remains debated.

Aims. Here, we offer a novel approach to disentangling the complex stellar populations within ω Cen based on phylogenetics methodologies from evolutionary biology.

Methods. These include the Gaussian mixture model and neighbor-joining clustering algorithms applied to a set of chemical abundances of ω Cen stellar members. Instead of using the classical approach in astronomy of grouping them into separate populations, we focused on how the stars are related to each other.

Results. We could identify stars that likely formed in globular clusters versus those originating from prolonged in-situ star formation and how these stars interconnect.

Conclusions. Our analysis supports the hypothesis that ω Cen might be a nuclear star cluster of a galaxy accreted by the Milky Way with a mass of about 10⁹ M_⊙. Furthermore, we revealed the existence of a previously unidentified in-situ stellar population with a distinct chemical pattern unlike any known population found in the Milky Way to date. Our analysis of ω Cen is an example of the success of cross-disciplinary research and shows the vast potential of applying evolutionary biology tools to astronomical datasets, opening new avenues for understanding the chemical evolution of complex stellar systems.

Key words: methods: statistical / stars: abundances / globular clusters: general / galaxies: star clusters: general

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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