Milky Way Tomography with K and M Dwarf Stars: the Vertical Structure of
  the Galactic Disk
  We use the number density distributions of K and M dwarf stars with vertical
height from the Galactic disk, determined using observations from the Sloan
Digital Sky Survey, to probe the structure of the Milky Way disk across the
survey's footprint. Using photometric parallax as a distance estimator we
analyze a sample of several million disk stars in matching footprints above and
below the Galactic plane, and we determine the location and extent of vertical
asymmetries in the number counts in a variety of thin- and thick-disk
subsamples in regions of some 200 square degrees within 2 kpc in vertical
distance from the Galactic disk. These disk asymmetries present wave-like
features as previously observed on other scales and at other distances from the
Sun. We additionally explore the scale height of the disk and the implied
offset of the Sun from the Galactic plane at different locations, noting that
the scale height of the disk can differ significantly when measured using stars
only above or only below the plane. Moreover, we compare the shape of the
number density distribution in the north for different latitude ranges with a
fixed range in longitude and find the shape to be sensitive to the selected
latitude window. We explain why this may be indicative of a change in stellar
populations in the latitude regions compared, possibly allowing access to the
systematic metallicity difference between thin- and thick-disk populations
through photometry.
