Maps of the parameters in the DR21 filament. Left two panels: the averaged velocity-integrated intensity ratio map of H₂CO 0.5 × [(3₂₂− 2₂₁ + 3₂₁ −2₂₀)/3₀₃−2₀₂] in the DR21 filament (see Sect. 3). The kinetic temperatures derived from the H₂CO line ratios (color bar in units of Kelvin). Right two panels: maps of nonthermal line width (color bar in units of km s⁻¹ ) and Mach number. The black stars and triangles show the locations of protostars (Davis et al. 2007) and the dense cores (Motte et al. 2007), respectively. The black circle and diamond illustrate the locations of the explosion center as described by Zapata et al. (2013) and the infrared-quiet massive dense core as delineated by Cao et al. (2019), respectively. Black contours show the integrated intensity of H₂CO 3₀₃−2₀₂ at 4.8 K km s⁻¹ (see Fig. 1).