Gaussian Processes, Median Statistics, Milky Way Rotation Curves
  We use the Iocco et al. (2015) compilation of 2,780 circular velocity
measurements to analyze the Milky Way rotation curve. We find that the error
bars for individual measurements are non-gaussian, and hence instead derive
median statistics binned central circular velocity values and error bars from
these data. We use these median statistics central values and error bars to fit
the data to simple, few parameter, rotation curve functions. These simple
functions are unable to adequately capture the significant small scale spatial
structure in these data and so provide poor fits. We introduce and use the
Gaussian Processes (GP) method to capture this small scale structure and use it
to derive Milky Way rotation curves from the binned median statistics circular
velocity data. The GP method rotation curves have significant small-scale
spatial structure superimposed on a broad rise to galactocentric radius
$R\approx7$ kpc and a decline at larger $R$. We use the GP method median
statistics rotation curve to measure the Oort $A$ and $B$ constants and other
characteristic rotation curve quantities. We study correlations in the residual
circular velocities (relative to the GP method rotation curve). Along with
other evidence for azimuthal asymmetry of the Milky Way circular rotation
velocity field, we find that larger residual circular velocities seem to favor
parts of spiral arms.
