Chemical & kinematic data of giants from APOGEE & Gaia

A Gaussian mixture model is employed to distinguish the high-{alpha} and low-{alpha} sequences along the metallicity by simultaneously using chemical and kinematical data. Four disk components are identified and quantified; they are named the h{alpha}mp, h{alpha}mr, l{alpha}mp, and l{alpha}mr disks and correspond to the high-{alpha} or low-{alpha}, and metal-poor or metal-rich properties.

Combined with the spatial and stellar-age information, we confirm that they are well interpreted by the two-infall formation model. The first infall of turbulent gas quickly forms the hot and thick h{alpha}mp disk with consequent thinner h{alpha}mr and l{alpha}mr disks. Then the second gas accretion forms a thinner and outermost l{alpha}mp disk.