Comparison between the C¹⁸O 2–1 (grey-scale), DCO⁺ 3–2 (dashed blue contours) and N₂D⁺ 3–2 toward the core. The lines are integrated from velocities of 3–7 km s^-1 (C¹⁸O and N₂D⁺) and 4–6 km s^-1 (DCO⁺). The dotted circles indicate the projected radii, where the dust temperature from radiative transfer calculations (Schöier et al. 2002; Jørgensen et al. 2005a) has dropped to 30 K and 20 K, respectively – assuming that the IRAS 16293A component is the sole source of luminosity and that the envelope is centered on this source.