Velocity-integrated intensity maps of deuterated and ¹³C-isotopologs. Top and middle rows: Ground-state emission of DCO⁺, DNC, and DCN observed with the CASCADE-program and follow-up mapping with the IRAM 30-m telescope. Bottom row: Maps for ¹³C-isotopologs. The intensities in the maps are integrated over the velocity range −7 km s⁻¹ to +0.5 km s⁻¹. HPBWs are displayed by the filled white circles in the lower left corner of each panel. For example, the HPBW beam-size is 34″ for the map showing DNC (2−1), 16″ for DCO⁺ (3−2) and 11″ for DCN (3−2). The white contours are showing levels of 4σ, 8σ and 12σ. The stars mark DR21 Main (red) and DR21(OH) (blue). The locations of the F1 and F3 sub-filament (Schneider et al. 2010) are indicated by dashed red and magenta curves, respectively.