Left: integrated intensity map of H¹³CN (2–1) line (gray scale) and DCN (2–1) line (contours) observed with NOEMA. Gray-scale levels start at 10% of the peak and increase in steps of 10%. The contour levels range from 3 to 15 in steps of three times the rms noise of the map, 6.5 mJy beam^-1 km s^-1. Red, blue, yellow, green, and cyan lines depict the regions used to extract the spectra and compute D_frac(HCN). These delineate the eastern wall (“E-wall” or B0e) of the cavity, B1a, B1e, the “head” of the bow-shock (B1c), and B1b, respectively. The synthesized beams of H¹³CN (2–1) and DCN (2–1) are shown in the bottom left and bottom right corner, respectively. Right: integrated intensity map of HDCO (2_1,1−1_0,1) line (gray scale, Fontani et al. 2014) and DCN (2–1) line using the same contour level as in the left panel. Gray-scale levels start at 40% of the HDCO peak and increase in steps of 10%. To highlight the bow-shock structure, we show the CH₃CN (8–7) K = 0−2 image (blue-dashed contours) from Codella et al. (2009). The synthesized beams of HDCO (2_1,1−1_0,1) and DCN (2–1) are shown in the bottom left and bottom right corner, respectively. In both panels the red cross indicates the peak of the high-velocity SiO (2–1) emission (Gueth et al. 1998).