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The chemical characterisation of halo substructure in the Milky Way based on APOGEE

Horta, D, Schiavon, RP, Mackereth, JT, Weinberg, DH, Hasselquist, S, Feuillet, D, O’Connell, RW, Anguiano, B, Allende-Prieto, C, Beaton, RL, Bizyaev, D, Cunha, K, Geisler, D, García-Hernández, DA, Holtzman, J, Jönsson, H, Lane, RR, Majewski, SR, Mészáros, S, Minniti, D , Nitschelm, C, Shetrone, M, Smith, VV and Zasowski, G (2022) The chemical characterisation of halo substructure in the Milky Way based on APOGEE. Monthly Notices of the Royal Astronomical Society, 520 (4). pp. 5671-5711. ISSN 0035-8711

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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, LMS-1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our main findings include: (i) the chemical properties of most substructures studied match qualitatively those of dwarf Milky Way satellites, such as the Sagittarius dSph. Exceptions are Nyx and Aleph, which are chemically similar to disc stars, implying that these substructures were likely formed in situ; (ii) Heracles differs chemically from in situ populations such as Aurora and its inner halo counterparts in a statistically significant way. The differences suggest that the star formation rate was lower in Heracles than in the early Milky Way; (iii) the chemistry of Arjuna, LMS-1, and I’itoi is indistinguishable from that of GES, suggesting a possible common origin; (iv) all three Sequoia samples studied are qualitatively similar. However, only two of those samples present chemistry that is consistent with GES in a statistically significant fashion; (v) the abundance patterns of the Helmi stream and Thamnos are different from all other halo substructures.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2022 Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Royal Astronomical Society
SWORD Depositor: A Symplectic
Date Deposited: 21 Nov 2022 13:30
Last Modified: 20 Mar 2023 16:45
DOI or ID number: 10.1093/mnras/stac3179
URI: https://researchonline.ljmu.ac.uk/id/eprint/18172
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