Moment-8,moment-9 and moment-2 maps (from left to right) of the CO (2−1) redshifted streamers of DR21: RF1, RF2, RF3 and RF4. The black contours represents the CO (2−1) emission at 5, 10, 15 and 20 times the rms noise level for each moment-8 map. The synthesized beam of the CO (2−1) map is shown within a box at the bottom right corner. The white arrow indicates the direction of the center of the explosive outflow.