A Map of the Local Velocity Substructure in the Milky Way Disk
  We confirm, quantify, and provide a table of the coherent velocity
substructure of the Milky Way disk within 2 kpc of the Sun towards the Galactic
anticenter, with 0.2 kpc resolution. We use the radial velocities of ~340,000
F-type stars obtained with the Guoshoujing Telescope (also known as the Large
Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST), and proper
motions derived from the PPMXL catalog. The PPMXL proper motions have been
corrected to remove systematic errors by subtracting the average proper motions
of galaxies and QSOs that have been confirmed in the LAMOST spectroscopic
survey, and that are within 2.5 degrees of the star's position. We provide the
resulting table of systematic offsets derived from the PPMXL proper motion
measurements of extragalactic objects identified in the LAMOST spectroscopic
survey. Using the corrected phase- space stellar sample, we find statistically
significant deviations in the bulk disk velocity of 20 km/s or more in the
three dimensional velocities of Galactic disk stars. The bulk velocity varies
significantly over length scales of half a kpc or less. The rotation velocity
of the disk increases by 20 km/s from the Sun's position to 1.5 kpc outside the
solar circle. Disk stars in the second quadrant, within 1 kpc of the Sun, are
moving radially towards the Galactic center and vertically towards a point a
few tenths of a kpc above the Galactic plane; looking down on the disk, the
stars appear to move in a circular streaming motion with a radius of order 1
kpc.
