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The GALAH Survey : chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3

Buder, Sven ; Lind, Karin ; Ness, Melissa and Feuillet, Diane LU orcid (2022) In Monthly Notices of the Royal Astronomical Society 510(2).
Abstract
Since the advent of Gaia astrometry, it is possible to identify massive accreted systems within the Galaxy through their unique dynamical signatures. One such system, Gaia-Sausage-Enceladus (GSE), appears to be an early 'building block' given its virial mass >1010M⊙ at infall (z ~ 1-3). In order to separate the progenitor population from the background stars, we investigate its chemical properties with up to 30 element abundances from the GALAH+ Survey Data Release 3 (DR3). To inform our choice of elements for purely chemically selecting accreted stars, we analyse 4164 stars with low-α abundances and halo kinematics. These are most different to the Milky Way stars for abundances of Mg, Si, Na, Al, Mn, Fe, Ni, and Cu. Based on the... (More)
Since the advent of Gaia astrometry, it is possible to identify massive accreted systems within the Galaxy through their unique dynamical signatures. One such system, Gaia-Sausage-Enceladus (GSE), appears to be an early 'building block' given its virial mass >1010M⊙ at infall (z ~ 1-3). In order to separate the progenitor population from the background stars, we investigate its chemical properties with up to 30 element abundances from the GALAH+ Survey Data Release 3 (DR3). To inform our choice of elements for purely chemically selecting accreted stars, we analyse 4164 stars with low-α abundances and halo kinematics. These are most different to the Milky Way stars for abundances of Mg, Si, Na, Al, Mn, Fe, Ni, and Cu. Based on the significance of abundance differences and detection rates, we apply Gaussian mixture models to various element abundance combinations. We find the most populated and least contaminated component, which we confirm to represent GSE, contains 1049 stars selected via [Na/Fe] versus [Mg/Mn] in GALAH+ DR3. We provide tables of our selections and report the chrono-chemodynamical properties (age, chemistry, and dynamics). Through a previously reported clean dynamical selection of GSE stars, including 30<JR/kpckms−1√<55 , we can characterize an unprecedented 24 abundances of this structure with GALAH+ DR3. With our chemical selection we characterize the dynamical properties of the GSE, for example mean JR/kpckms−1√= 26+9−14 . We find only (29±1) per cent of the GSE stars within the clean dynamical selection region. Our methodology will improve future studies of accreted structures and their importance for the formation of the Milky Way. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Monthly Notices of the Royal Astronomical Society
volume
510
issue
2
publisher
Oxford University Press
external identifiers
  • scopus:85124281979
ISSN
1365-2966
DOI
10.1093/mnras/stab3504
language
English
LU publication?
yes
id
a73f5151-8eec-4016-933f-6f905e921b33
date added to LUP
2022-03-03 13:43:26
date last changed
2024-05-16 11:09:17
@article{a73f5151-8eec-4016-933f-6f905e921b33,
  abstract     = {{Since the advent of Gaia astrometry, it is possible to identify massive accreted systems within the Galaxy through their unique dynamical signatures. One such system, Gaia-Sausage-Enceladus (GSE), appears to be an early 'building block' given its virial mass  &gt;1010M⊙  at infall (z ~ 1-3). In order to separate the progenitor population from the background stars, we investigate its chemical properties with up to 30 element abundances from the GALAH+ Survey Data Release 3 (DR3). To inform our choice of elements for purely chemically selecting accreted stars, we analyse 4164 stars with low-α abundances and halo kinematics. These are most different to the Milky Way stars for abundances of Mg, Si, Na, Al, Mn, Fe, Ni, and Cu. Based on the significance of abundance differences and detection rates, we apply Gaussian mixture models to various element abundance combinations. We find the most populated and least contaminated component, which we confirm to represent GSE, contains 1049 stars selected via [Na/Fe] versus [Mg/Mn] in GALAH+ DR3. We provide tables of our selections and report the chrono-chemodynamical properties (age, chemistry, and dynamics). Through a previously reported clean dynamical selection of GSE stars, including  30&lt;JR/kpckms−1√&lt;55 , we can characterize an unprecedented 24 abundances of this structure with GALAH+ DR3. With our chemical selection we characterize the dynamical properties of the GSE, for example mean  JR/kpckms−1√=  26+9−14 . We find only  (29±1) per cent  of the GSE stars within the clean dynamical selection region. Our methodology will improve future studies of accreted structures and their importance for the formation of the Milky Way.}},
  author       = {{Buder, Sven and Lind, Karin and Ness, Melissa and Feuillet, Diane}},
  issn         = {{1365-2966}},
  language     = {{eng}},
  number       = {{2}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{The GALAH Survey : chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3}},
  url          = {{http://dx.doi.org/10.1093/mnras/stab3504}},
  doi          = {{10.1093/mnras/stab3504}},
  volume       = {{510}},
  year         = {{2022}},
}