Observed ¹²CO (2–1) emission in the CI Tau disk. Shown are the channel map of the observed line brightness distribution (top left), the moment–zero map (top right), and the integrated spectrum (top middle). The channel map shows 16 velocity channels with a step of 0.5 km s⁻¹ in the [−4.5, +4.5] km s⁻¹ range around the systemic velocity. The contour lines start at 2 K, with a step of 2 K. The color bar shows line brightness temperatures (K). The contour lines in the moment–zero plot start at 3, 6, and 9σ with a step of 6σ afterward. The lσ rms noise (mJy km s⁻¹) is shown in the upper left corner of the moment–zero plot, and the synthesized beam is depicted by the dark ellipse in the left bottom corner. The ¹²CO (2–1) spectrum shows a nearly absent blueshiſted velocity component due to the cloud absorption.