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Astrophysics > Astrophysics of Galaxies
Title: The metal-weak Milky Way stellar disk hidden in the Gaia-Sausage-Enceladus debris: the APOGEE DR17 view
(Submitted on 28 Feb 2023 (v1), last revised 27 Jun 2023 (this version, v2))
Abstract: We have for the first time identified the early stellar disk in the Milky Way by using a combination of elemental abundances and kinematics. Using data from APOGEE DR17 and Gaia we select stars in the Mg-Mn-Al-Fe plane with elemental abundances indicative of accreted origin and find stars with both halo-like and disk-like kinematics. The stars with halo-like kinematics lie along a lower sequence in [Mg/Fe], while the stars with disk-like kinematics lie along a higher sequence. Through with asteroseismic observations, we determine the stars with halo-like kinematics are old, 9-11 Gyr and that the more evolved stellar disk is about 1-2 Gyr younger. We show that the in situ fraction of stars on deeply bound orbits is not small, in fact the inner Galaxy likely harbours a genuine in-situ population together with an accreted one. In addition, we show that the selection of Gaia-Sausage-Enceladus in the En-Lz plane is not very robust. In fact, radically different selection criteria give almost identical elemental abundance signatures for the accreted stars.
Submission history
From: Diane Feuillet [view email][v1] Tue, 28 Feb 2023 19:00:03 GMT (8149kb,D)
[v2] Tue, 27 Jun 2023 14:03:30 GMT (8862kb,D)
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