Left: circular velocity field for the contribution of luminous matter only. Middle: zoom in the inner 4 kpc with contours representing the emission from molecular gas. A dashed circle shows the location of R = 2.2h_⋆ = 3.7 kpc, where h_⋆ is the stellar disk scalelength. Right: variation of velocity with azimuth at R = 3.7 kpc. Open circles represent the velocities of four points inside, down- and upstream of the spiral arms, indicated with white filled circles in the middle panel. The dashed line is the axisymmetric value. The velocity scale of the left axis is for luminous matter only, while that of the right axis takes an additional contribution from dark matter into account.