Position-velocity diagram for CO J = 2–1. Each panel is a cut at a different height above the plane (indicated in the lower right corner of each panel). The spatial resolution is 56 au. Top: without the background added (spectral resolution 0.08 km s^-1). Bottom: with the background spectrum added. In each panel, the black line highlights the apparent inner radius whose value is quoted in the upper left corner. Here, the spectral resolution is 0.27 km s^-1.