Vertical gradient of rotation of MW in a finite-width disk model with a Mexican hat vertical profile as a function of the radial variable, shown for various width-scales h and altitudes z above the mid-plane. Top panel: gradient at an altitude of 100 pc; – h = 100 pc (dashed line), – h = 117 pc (solid line), and h = 150 pc (uppermost dash-dotted line). (For comparison, the (dash-dotted line) in the middle shows the gradient in a disk model with the vertical exponential profile and the width-scale h′ = 88 pc at the same altitude.) Upper middle panel: vertical gradient of rotation at various altitudes for h = 117 pc. To enable the comparison of structures in the vertical gradient with those in the rotation curve and in the column mass density, Lower middle panel: MW rotation curve, and bottom panel: column mass density for a finite-width disk model with a Mexican hat vertical profile (h = 117 pc).