Deviations from Keplerian rotation for ¹³CO(3−2) synthetic images of the post-processed simulations, for a VSI-unstable disk without embedded planets. In the first row, from left to right, we show models including the full disk, only the disk hemisphere closest to the observer (front side), and the farthest hemisphere of the disk (back side), for a disk inclination of 30 degrees. In the second row, a deprojected view of the residual maps (first row) is shown. The fourth panel, shows a normalized square root of the absolute value of the product of the front and back side deprojected residual maps, multiplied the sign of the initial multiplication of both residuals (see Eq. (9)). A ring of interest is enclosed by black dashed lines, drawn at 1.55 and 1.85 arcsec. The black solid line along the semi-minor axis in the non-Keplerian residuals shows the line of zero gas velocity projected into the line of sight.