We report a detailed investigation of the bulk motions of the nearby Galactic stellar disk , based on three samples selected from the LSS-GAC DR2 : a global sample containing 0.57 million FGK dwarfs out to \sim 2 kpc , a local subset of the global sample consisting \sim 5,400 stars within 150 pc , and an anti-center sample containing \sim 4,400 AFGK dwarfs and red clump stars within windows of a few degree wide centered on the Galactic anti-center .
The global sample is used to construct a three-dimensional map of bulk motions of the Galactic disk from the solar vicinity out to \sim 2 kpc with a spatial resolution of \sim 250 pc .
Typical values of the radial and vertical components of bulk motion range from - 15 km s ^ { -1 } to 15 km s ^ { -1 } , while the lag behind the circular speed dominates the azimuthal component by up to \sim 15 km s ^ { -1 } .
The map reveals spatially coherent , kpc-scale stellar flows in the disk , with typical velocities of a few tens km s ^ { -1 } .
Bending- and breathing-mode perturbations are clearly visible , and vary smoothly across the disk plane .
Our data also reveal higher-order perturbations , such as breaks and ripples , in the profiles of vertical motion versus height .
From the local sample , we find that stars of different populations exhibit very different patterns of bulk motion .
Finally , the anti-center sample reveals a number of peaks in stellar number density in the line-of-sight velocity versus distance distribution , with the nearer ones apparently related to the known moving groups .
The “ velocity bifurcation ” reported by Liu et al .
( 2012 ) at Galactocentric radii 10–11 kpc is confirmed .
However , just beyond this distance , our data also reveal a new triple-peaked structure .