Abstract
The Gaia mission has revolutionised our ability to study the Milky Way. In this thesis, we combine kinematic data from Gaia, with age information and chemical compositions, to further our understanding of the accreted debris in the local halo. Stars from a single accretion event are deposited onto similar orbits. Since orbits can be characterised by their integrals of motion such as energy or angular momenta, we can thus search for the stellar debris of past accretion events by looking for over-densities in integrals of motion space. We developed and applied a novel clustering algorithm to identify such substructures in the local stellar halo. Using chemical abundances from APOGEE and LAMOST we characterise these substructures, some of which are of in situ and others of accreted origin. We then follow up several of the new and tight substructures of interest with high-resolution spectroscopy. The chemical and dynamical data indicate that most of these are accreted. We characterise two of the larger substructures using colour-magnitude diagram (CMD) fitting techniques to derive age and metallicity distributions of the stars in these substructures, unveiling slight differences in their progenitor’s evolution and accretion times. We also investigate the ED-2 stream and its association with the 33 M⊙ Gaia black hole (BH3), providing the first clear evidence linking a black hole to a disrupted star cluster. This thesis presents the updated view of the assembly history of the Milky Way that emerges from the third Gaia data release.
Original language | English |
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Qualification | Doctor of Philosophy |
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Award date | 10-Dec-2024 |
Place of Publication | [Groningen] |
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Publication status | Published - 2024 |