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.Comment: 32 pages, 19 figures, accepted to Ap