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
  We explore the contribution of the Gaia-Sausage to the stellar halo of the
Milky Way by making use of a Gaussian Mixture model (GMM) and applying it to
halo star samples of LAMOST K giants, SEGUE K giants, and SDSS blue horizontal
branch stars. The GMM divides the stellar halo into two parts, of which one
represents a more metal-rich and highly radially biased component associated
with an ancient, head-on collision referred to as the Gaia-Sausage, and the
other one is a more metal-poor and isotropic halo. A symmetric bimodal Gaussian
is 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 decreases
with 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 decline
beyond $r_\mathrm{gc} \sim$ $25-30$ kpc, and the outer halo is found to be
significantly less influenced by the Gaia-Sausage than the inner halo. After
the removal of halo substructures found by integrals of motion, the
contribution 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 several
possible Sausage-related substructures consisting of stars on highly eccentric
orbits. The GMM/Sausage component agrees well with the selected substructure
stars in their chemodynamical properties, which increases our confidence in the
reliability of the GMM fits.
