The positions of CO (2−1) condensations in DR21. The background grayscale image and the green contours (at 5, 10, 15, and 20 times the rms noise level of 0.06 mJy beam⁻¹) are the ALMA 1.3 mm continuum image from Figure 2. The red and blue circles correspond to the position of red-and blueshifted CO(2−1) gas condensation that is identified in the velocity cube. The yellow square denotes the position of the explosion center. The synthesized beam is depicted within a box in the bottom right corner. The central position is located at (0″, 0″), corresponding to RA=20^h39^m01^s.1 and Dec=+42°19′ 37″.9.