Overview of the DR21 Main high-mass star-forming region. Overlay of the H41α emission from DR21 integrated between −30 and 30 km s⁻¹ (orange dashed contours) on HCO⁺ 1–0 observations (colors) from IRAM 30 m and NOEMA (beam sizes of 2.60^′′ × 2.36^′′ and 3.29^′′ × 2.74^′′, respectively; Skretas et al. 2023). The yellow rectangle shows the interaction region (Skretas et al. 2023), and the light blue rectangle shows the field of view of the FIFI-LS observations. The magenta star shows the center of the DR21-1 core at (α, δ)_J2000=(20^h39^m01^s.03,+42^∘19^′33^′′.8) following Cao et al. (2019) and the magenta arrows the outflow direction based on the HCO⁺map (Skretas et al. 2023). The map also shows six positions of radio continuum sources identified as OB stars by Roelfsema et al. 1989 (red points), the 95 GHz methanol masers (brown squares) from Plambeck & Menten (1990), the 22 GHz H₂ O maser (black triangle) from Genzel & Downes (1977), and the H₂ peaks (white × symbols) (Garden et al. 1986).