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The detailed chemical abundance patterns of accreted halo stars from the optical to infrared

Carrillo, Andreia; Hawkins, Keith; Jofré, Paula; de Brito Silva, Danielle; Das, Payel; Lucey, Madeline

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Authors

Keith Hawkins

Paula Jofré

Danielle de Brito Silva

Payel Das

Madeline Lucey



Abstract

Understanding the assembly of our Galaxy requires us to also characterize the systems that helped build it. In this work, we accomplish this by exploring the chemistry of accreted halo stars from Gaia-Enceladus/Gaia-Sausage (GES) selected in the infrared from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) Data Release 16. We use high resolution optical spectra for 62 GES stars to measure abundances in 20 elements spanning the α, Fe-peak, light, odd-Z, and notably, the neutron-capture groups of elements to understand their trends in the context of and in contrast to the Milky Way and other stellar populations. Using these derived abundances we find that the optical and the infrared abundances agree to within 0.15 dex except for O, Co, Na, Cu, and Ce. These stars have enhanced neutron-capture abundance trends compared to the Milky Way, and their [Eu/Mg] and neutron-capture abundance ratios (e.g. [Y/Eu], [Ba/Eu], [Zr/Ba], [La/Ba], and [Nd/Ba]) point to r-process enhancement and a delay in s-process enrichment. Their [α/Fe] trend is lower than the Milky Way trend for [Fe/H] > −1.5 dex, similar to previous studies of GES stars and consistent with the picture that these stars formed in a system with a lower rate of star formation. This is further supported by their depleted abundances in Ni, Na, and Cu abundances, again, similar to previous studies of low-α stars with accreted origins.

Citation

Carrillo, A., Hawkins, K., Jofré, P., de Brito Silva, D., Das, P., & Lucey, M. (2022). The detailed chemical abundance patterns of accreted halo stars from the optical to infrared. Monthly Notices of the Royal Astronomical Society, 513(2), 1557-1580. https://doi.org/10.1093/mnras/stac518

Journal Article Type Article
Acceptance Date Feb 21, 2022
Online Publication Date Apr 28, 2022
Publication Date 2022-06
Deposit Date Jun 23, 2022
Publicly Available Date Mar 28, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 513
Issue 2
Pages 1557-1580
DOI https://doi.org/10.1093/mnras/stac518

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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.




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