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We explore the contribution of the Gaia-Sausage to the stellar halo of theMilky Way by making use of a Gaussian Mixture model (GMM) and applying it tohalo star samples of LAMOST K giants, SEGUE K giants, and SDSS blue horizontalbranch stars. The GMM divides the stellar halo into two parts, of which onerepresents a more metal-rich and highly radially biased component associatedwith an ancient, head-on collision referred to as the Gaia-Sausage, and theother one is a more metal-poor and isotropic halo. A symmetric bimodal Gaussianis used to describe the distribution of spherical velocity of the Gaia-Sausage,and we find that the mean absolute radial velocity of the two lobes decreaseswith Galactocentric radius. We find that the Gaia-Sausage contributes about$41\%-74\%$ of the inner (Galactocentric radius $r_\mathrm{gc} < 30$ kpc)stellar halo. The fraction of stars of the Gaia-Sausage starts to declinebeyond $r_\mathrm{gc} \sim$ $25-30$ kpc, and the outer halo is found to besignificantly less influenced by the Gaia-Sausage than the inner halo. Afterthe removal of halo substructures found by integrals of motion, thecontribution of the \textit{Gaia}-Sausage falls slightly within $r_\mathrm{gc}\sim$ 25 kpc, but is still as high as $30\%-63\%$. Finally, we select severalpossible Sausage-related substructures consisting of stars on highly eccentricorbits. The GMM/Sausage component agrees well with the selected substructurestars in their chemodynamical properties, which increases our confidence in thereliability of the GMM fits.

astrophysical journal/the astrophysical journal

Contribution of Gaia Sausage to the Galactic Stellar Halo Revealed by K  Giants and Blue Horizontal Branch Stars from the Large Sky Area Multi-Object  Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and Gaia