We report an analysis of the metal-rich tail ( [ Fe/H ] > -0.75 ) of stars located at distances from the Galactic plane up to |z| \sim 10 kpc , observed by the Apache Point Observatory Galactic Evolution Experiment ( APOGEE ) .
We examine the chemistry , kinematics , and dynamics of this metal-rich sample using chemical abundances and radial velocities provided by the fourteenth APOGEE data release ( DR14 ) and proper motions from the second Gaia data release ( DR2 ) .
The analysis reveals three chemically different stellar populations in the [ Mg/Fe ] vs. [ Fe/H ] space – a high- [ Mg/Fe ] and low- [ Mg/Fe ] populations , and a third group with intermediate [ Mg/Fe ] \sim +0.1 – as well as for other chemical elements .
We find that they are also kinematically and dynamically distinct .
The high- [ Mg/Fe ] population exhibits a prograde rotation which decreases down to 0 as |z _ { max } | increases , as well as eccentric orbits that are more bound and closer to the plane .
The low- [ Mg/Fe ] stars are likely Sagittarius members , moving in less-bound orbits reaching larger distances from the centre and the Galactic plane .
The intermediate-Mg stars resembles the two stellar overdensities lying about |z| \sim 5 kpc recently reported in the literature , for which a disc origin has been claimed .
We report the identification of new members of these two disc-heated overdensities .