On the kinematic signature of the Galactic warp as revealed by the
  LAMOST-TGAS data
  Using a sample of about 123,000 stars with accurate 3D velocity measurements
from the LAMOST-TGAS data, we confirm the kinematic signature of the Galactic
warp found by Sch\"onrich & Dehnen recently. The data reveal a clear trend of
increasing mean vertical velocity $\overline{V_{z}}$ as a function of absolute
vertical angular momentum $L_{z}$ and azimuthal velocity $V_{\phi}$ for guiding
center radius $R_{g}$ between 6.0 and 10.5 kpc. The trend is consistent with a
large-scale Galactic warp. Similar to Sch\"onrich & Dehnen, we also find a
wave-like pattern of $\overline{V_{z}}$ versus $L_{z}$ with an amplitude of
$\sim 0.9$ km s$^{-1}$ on a scale of $\sim 2.0$ kpc, which could arise from
bending waves or a winding warp. Finally, we confirm a prominent, localized
peak in $\overline{V_z}$ near $L_z \sim 2150$ kpc km s$^{-1}$ (corresponding to
$R_{g} \sim 9$ kpc and $V_{\phi} \sim 255$ km s$^{-1}$). The additional
line-of-sight velocity information from LAMOST reveals that stars in this
feature have a large, inward radial velocity of $V_{R} \sim -13.33 \pm 0.59$ km
s$^{-1}$ and a small radial velocity dispersion $\sigma_{R} \sim 25.27 \pm
0.89$ km s$^{-1}$, suggesting that a stellar stream gives rise to this feature.
