The imprint of arms and bars on rotation curves: in-plane and off-plane
  Within Rotation Curves (RC) is encoded the kinematical state of the stellar
disc as well as information about the dynamical mechanisms driving the secular
evolution of galaxies. To explain the characteristic features of RCs that arise
by the influence of spiral patterns and bar, we study the kinematics of the
stellar disc in a set of spiral galaxy models specifically tailored for this
purpose. We find that, for our models, the induced non-circular motions are
more prominent for spirals with larger pitch angle, the ones typical in late
type galaxies. Moreover, inside corotation, stars rotate slower along the
spiral arms than along the inter-arm, which translates into a local minima or
maxima in the RC, respectively. We also see, from off-plane RC, that the
rotation is faster for stars that at observed closer to the plane, and
diminishes as one looks farther off plane; this trend is more noticeable in our
Sa galaxy model than our Sc galaxy model. Additionally, in a previous work we
found that the diagonal ridges in the $V_{\phi}-R$ plane, revealed through the
Gaia DR2, have a resonant origin due to the spiral arms and bar and that these
ridges project themselves as wiggles in the RC; here, we further notice that
the development of these ridges, and the development of high orbital
eccentricities in the stellar disc are the same. Hence, we conclude that, the
following explanations of bumps and wiggles in RCs are equivalent: they are
manifestations of diagonal ridges in the $V_{\phi}-R$ plane, or of the
rearrangement of the orbital eccentricities in the stellar disc.
