Age dating of an early Milky Way merger via asteroseismology of the naked-eye star ν Indi

Chaplin, William J.; Serenelli, Aldo M.; Miglio, Andrea; Morel, Thierry; Mackereth, J. Ted; Vincenzo, Fiorenzo; Kjeldsen, Hans; Basu, Sarbani; Ball, Warrick H.; Stokholm, Amalie; Verma, Kuldeep; Mosumgaard, Jakob Rørsted; Silva Aguirre, Victor; Mazumdar, Anwesh; Ranadive, Pritesh; Antia, H. M.; Lebreton, Yveline; Ong, Joel; Appourchaux, Thierry; Bedding, Timothy R.; Christensen-Dalsgaard, Jørgen; Creevey, Orlagh; García, Rafael A.; Handberg, Rasmus; Huber, Daniel; Kawaler, Steven D.; Lund, Mikkel N.; Metcalfe, Travis S.; Stassun, Keivan G.; Bazot, Michäel; Beck, Paul G.; Bell, Keaton J.; Bergemann, Maria; Buzasi, Derek L.; Benomar, Othman; Bossini, Diego; Bugnet, Lisa; Campante, Tiago L.; Orhan, Zeynep Çelik; Corsaro, Enrico; González-Cuesta, Lucía; Davies, Guy R.; Di Mauro, Maria Pia; Egeland, Ricky; Elsworth, Yvonne P.; Gaulme, Patrick; Ghasemi, Hamed; Guo, Zhao; Hall, Oliver J.; Hasanzadeh, Amir; Hekker, Saskia; Howe, Rachel; Jenkins, Jon M.; Jiménez, Antonio; Kiefer, René; Kuszlewi...

Abstract

Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies1. Although these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to date precisely the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called Gaia–Enceladus1, leading to substantial pollution of the chemical and dynamical properties of the Milky Way. Here we identify the very bright, naked-eye star ν Indi as an indicator of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be 11.0±0.7 (stat) ±0.8 (sys) billion years. The star bears hallmarks consistent with having been kinematically heated by the Gaia–Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 billion years ago, at 68% and 95% confidence, respectively. Computations based on hierarchical cosmological models slightly reduce the above limits.

Citation

Chaplin, W. J., Serenelli, A. M., Miglio, A., Morel, T., Mackereth, J. T., Vincenzo, F., Kjeldsen, H., Basu, S., Ball, W. H., Stokholm, A., Verma, K., Mosumgaard, J. R., Silva Aguirre, V., Mazumdar, A., Ranadive, P., Antia, H. M., Lebreton, Y., Ong, J., Appourchaux, T., Bedding, T. R., …Yıldız, M. (2020). Age dating of an early Milky Way merger via asteroseismology of the naked-eye star ν Indi. Nature Astronomy, 4(4), 382-389. https://doi.org/10.1038/s41550-019-0975-9

• Journal Article Type: Article
• Acceptance Date: Nov 13, 2019
• Online Publication Date: Jan 13, 2020
• Publication Date: 2020-04
• Deposit Date: Mar 12, 2022
• Publicly Available Date: Mar 31, 2022
• Journal: Nature Astronomy
• Publisher: Nature Research
• Peer Reviewed: Peer Reviewed
• Volume: 4
• Issue: 4
• Pages: 382-389
• DOI: https://doi.org/10.1038/s41550-019-0975-9
• Keywords: Galaxies and clusters; Stars
• Public URL: https://hull-repository.worktribe.com/output/3947941
• Related Public URLs: https://eprints.keele.ac.uk/7573/