The Imprint of Spiral Arms on the Galactic Rotation Curve
  We discuss a model for the Milky Way obtained by fitting the observed
terminal velocities with the radial acceleration relation. The resulting
stellar surface density profile departs from a smooth exponential disk, having
bumps and wiggles that correspond to massive spiral arms. These features are
used to estimate the term for the logarithmic density gradient in the Jeans
equation, which turn out to have exactly the right location and amplitude to
reconcile the apparent discrepancy between the stellar rotation curve and that
of the interstellar gas. This model also predicts a gradually declining
rotation curve outside the solar circle with slope
$-1.7\;\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{kpc}^{-1}$, as subsequently
observed.
