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Chemically characterising the Milky Way’s stellar halo

Published online by Cambridge University Press:  13 February 2024

Danny Horta*
Affiliation:
Astrophysics Research Institute, Liverpool John Moores University, Liverpool Brownlow Hill,L3 5RF, UK Center for Computational Astrophysics, Flatiron Institute, 162 5th Ave., New York, NY 10010, USA
Ricardo P. Schiavon
Affiliation:
Astrophysics Research Institute, Liverpool John Moores University, Liverpool Brownlow Hill,L3 5RF, UK
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Abstract

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Galactic haloes in a Λ-CDM universe are predicted to host today a swarm of debris resulting from cannibalised dwarf galaxies. The chemo-dynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and Gaia, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, Gaia-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our results show that many halo substructures conjectured to be debris from individual accretions likely belong to either the omnipresent GES or to in situ populations, and that the Milky Way likely underwent three major mergers so far: Heracles, GES, Sagittarius dSph.

Type
Contributed Paper
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2024. Published by Cambridge University Press on behalf of International Astronomical Union

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