ALMA channels map of AS 209. The figure shows selected velocity channels of ¹²CO J = 2−1 (top) and ¹³CO J = 2−1 (bottom). Each panel shows the line emission in a given channel centered at the velocity reported in the top-right corner. The dotted ellipses represent the orbital distances of r = 100 au and r = 200 au at z = 0. The Keplerian isovelocity region was overlaid for the top (solid line) and bottom (dashed) surfaces (see Sect. 3). The arrows point to the deviation from Keplerian velocity. The deviation is detected in multiple channels and over a wide range of azimuth angles both in the ¹²CO and in the ¹³CO channels maps.