Simulated images of CO(J = 2−1) emission of HD 138813 in three different configurations. In the first column, the disk does not host any planet and is to be compared to the two other columns where a Jupiter-mass planet (center) and a five-Jupiter-mass planet (right) have been introduced in the disk at 70 AU. Moment-zero maps are shown in the top row, and single-channel maps at dv = −1.4 km/s are shown in the bottom row. In the smooth-disk case, the lobe shape emission is continuous, whereas the gap produced by the planets cuts the emission, making the gap observable.