Partitioning the Galactic halo with Gaussian Mixture Models

The Galactic halo is supposed to form from merging with nearby dwarf galaxies. In order probe different components of the halo, we have applied Gaussian Mixture Models method a selected sample metal poor stars [Fe/H] $< -0.7$ dex in APOGEE DR16 catalogue based on four-parameters, metallicity, [Mg/Fe] ratio and spatial velocity (\textit{$V_R$, $V_\phi$}). Nine groups are identified four (group 1, 3, 4 5), one thick disk 6), thin 8) galaxies 7) by analyzing their distributions ([M/H], [Mg/Fe]), ($V_R$, $V_\phi$), (\textit{Zmax}, \textit{eccentricity}), (\textit{Energy}, \textit{Lz}) ([Mg/Mn], [Al/Fe]) coordinates. rest two respectively caused observational effect 9) cross section component 2) between disk. It found that extremely outer accreted 1), born Milky Way can not be distinguished those other either chemically or kinematically. intermediate metallicity $-$1.6 $<$ dex, mainly composed Gaia-Enceladus-Sausage substructure which easily group (the in-situ group) both chemical kinematic space. Some may come some scattered high orbits resonant effects as shown \textit{Zmax} versus Energy coordinate. We also displayed distribution main do show clear relation radius.