Metallicity and Kinematics of the Galactic halo from the LAMOST sample
  stars
  We study the metallicity distribution and kinematic properties of 4,680
A/F/G/K-type giant stars with $|z|>$ 5 kpc selected from the LAMOST
spectroscopic survey. The metallicity distribution of giant stars with 5
$<|z|\leqslant$ 15 kpc can be described by a three-peak Gaussian model with
peaks at [Fe/H] $\sim-0.6\pm0.1$, $-1.2\pm0.3$ and $-2.0\pm0.2$, corresponding
to the ratio of 19$\%$, 74$\%$ and 7$\%$, respectively. The $\rm{[\alpha/Fe]}$
is used to associate the three peaks with the thick disk, inner-halo and
outer-halo components of the Galaxy. The metallicity distribution of these
giant stars, which is fit with Gaussians corresponding to the three components,
show a growing fraction of inner-halo component and declining fraction of the
thick-disk component with increasing distance from the Galactic plane. Adopting
a galaxy potential model, we also derive the orbital parameters of the sample
stars, such as orbit eccentricity and rotation velocity. The peak values of
derived orbital eccentricity for stars covering different metallicity regions
maintain $e\sim$ 0.75, independent of height above the plane, within the range
5$<|z|<$ 15 kpc. By comparing the MDFs of stars in different rotation velocity
intervals, we find that the majority of the retrograde stars are more
metal-poor than the prograde stars.
