TY - JOUR
T1 - The GALAH Survey
T2 - chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3
AU - The GALAH collaboration
AU - Buder, Sven
AU - Lind, Karin
AU - Ness, Melissa K.
AU - Feuillet, Diane K.
AU - Horta, Danny
AU - Monty, Stephanie
AU - Buck, Tobias
AU - Nordlander, Thomas
AU - Bland-Hawthorn, Joss
AU - Casey, Andrew R.
AU - De Silva, Gayandhi M.
AU - D'Orazi, Valentina
AU - Freeman, Ken C.
AU - Hayden, Michael R.
AU - Kos, Janez
AU - Martell, Sarah L.
AU - Lewis, Geraint F.
AU - Lin, Jane
AU - Schlesinger, Katharine J.
AU - Sharma, Sanjib
AU - Simpson, Jeffrey D.
AU - Stello, Dennis
AU - Zucker, Daniel B.
AU - Zwitter, Tomaž
AU - Ciucă, Ioana
AU - Horner, Jonathan
AU - Kobayashi, Chiaki
AU - Ting, Yuan-Sen
AU - Wyse, Rosemary F. G.
N1 - This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 510, Issue 2, February 2022, Pages 2407–2436, https://doi.org/10.1093/mnras/stab3504. Copyright 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
PY - 2022/2/1
Y1 - 2022/2/1
N2 - 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/kpc kms−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/kpc kms−1=26+9−14. We find only (29±1) per cent(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.
AB - 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/kpc kms−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/kpc kms−1=26+9−14. We find only (29±1) per cent(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.
KW - Galaxy: abundances
KW - Galaxy: formation
KW - Galaxy: halo
KW - Galaxy: kinematics and dynamics
UR - http://www.scopus.com/inward/record.url?scp=85124281979&partnerID=8YFLogxK
U2 - 10.1093/mnras/stab3504
DO - 10.1093/mnras/stab3504
M3 - Article
AN - SCOPUS:85124281979
SN - 0035-8711
VL - 510
SP - 2407
EP - 2436
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -