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Chasing the impact of the Gaia-Sausage-Enceladus merger on the formation of the Milky Way thick disc

Ciucă, Ioana; Kawata, Daisuke; Ting, Yuan-Sen; Grand, Robert JJ; Miglio, Andrea; Hayden, Michael; Baba, Junichi; ... Freeman, Ken; + view all (2023) Chasing the impact of the Gaia-Sausage-Enceladus merger on the formation of the Milky Way thick disc. Monthly Notices of the Royal Astronomical Society: Letters , Article slad033. 10.1093/mnrasl/slad033. (In press). Green open access

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Abstract

We employ our Bayesian Machine Learning framework BINGO (Bayesian INference for Galactic archaeOlogy) to obtain high-quality stellar age estimates for 68,360 red giant and red clump stars present in the 17th data release of the Sloan Digital Sky Survey, the APOGEE-2 high-resolution spectroscopic survey. By examining the denoised age-metallicity relationship of the Galactic disc stars, we identify a drop in metallicity with an increase in [Mg/Fe] at an early epoch, followed by a chemical enrichment episode with increasing [Fe/H] and decreasing [Mg/Fe]. This result is congruent with the chemical evolution induced by an early-epoch gas-rich merger identified in the Milky Way-like zoom-in cosmological simulation Auriga. In the initial phase of the merger of Auriga 18 there is a drop in metallicity due to the merger diluting the metal content and an increase in the [Mg/Fe] of the primary galaxy. Our findings suggest that the last massive merger of our Galaxy, the Gaia-Sausage-Enceladus, was likely a significant gas-rich merger and induced a starburst, contributing to the chemical enrichment and building of the metal-rich part of the thick disc at an early epoch.

Type: Article
Title: Chasing the impact of the Gaia-Sausage-Enceladus merger on the formation of the Milky Way thick disc
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnrasl/slad033
Publisher version: https://doi.org/10.1093/mnrasl/slad033
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Galaxy: formation, Galaxy: abundances, asteroseismology
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10168176
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