Kinematic moment-1 maps for the J = 2 − 1 transition of ¹²CO in the shadow-driven spiral simulations. Here the initial and final maps are plotted separately, unlike in the other figures where the former is used as a background model and subtracted from the latter. Accordingly, the range of the color scale (−5 km s⁻¹ ≤ v_⊥ ≤ 5 km s⁻¹ ) was expanded to accommodate the Keplerian flow of the disk.