Milky Way kinematics. II.

We use these data, together with our previous work on the fourth Galactic quadrant, to produce a densely sampled, uniformly measured, rotation curve of the northern and southern Milky Way between 3kpc<R<8kpc. We determine a new joint rotation curve fit for the first and fourth quadrants, which is consistent with the fit we published in McClure-Griffiths & Dickey (Paper I, 2007ApJ...671..427M) and can be used for estimating kinematic distances interior to the solar circle.

Structure in the rotation curves is now exquisitely well defined, showing significant velocity structure on lengths of ~200pc, which is much greater than the spatial resolution of the rotation curve. Furthermore, the shape of the rotation curves for the first and fourth quadrants, even after subtraction of a circular rotation fit shows a surprising degree of correlation with a roughly sinusoidal pattern between 4.2<R<7kpc.