Ideal ¹²C¹⁸O (3−2) velocity-channel map of a T Tauri disk model with an embedded Jupiter-mass planet (at 80 AU). The disk mass amounts to 2.67 × 10^-3 M_⊙ and the outer radius is 144 AU. The flux density in Jy/as² is color coded for each individual channel. The disk is seen face-on. Mostly because of the low abundance of this CO isotopologue, this line traces deeper parts of the disk. Thus, the gap is clearly detectable in contrast to the optically thick ¹²C¹⁶O line of this model (cf. Fig. 2).