Velocity maps of C¹⁷O (3−2), H¹³CO+ (4−3), N₂D+ (4−3), and N₂H+ (3−2). Top panels: moment 0 maps of the respective transitions are shown in grayscale. The overlaid contours show the red-shifted and blue-shifted emission in steps of 0.1 km s⁻¹ with respect to the systematic velocity of the source (υ_LSR = 4 km s⁻¹, displayed in white). Integration ranges consider emission between 2-6 km s⁻¹ for C¹⁷O (3−2) and H¹³CO⁺ (4−3). Smaller velocity intervals of 2.5 − 5 km s⁻¹ and 2.3-5 km s⁻¹ are chosen for N₂D⁺ (4−3) and N₂H⁺ (3−2) respectively, in order to exclude nearby HDCO emission and the resolved hyperfine components of N₂H⁺. Bottom panels: moment 1 maps of the molecules shown in the top panels. Contours of the moment 0 maps are drawn at 3σ, in steps of 2σ between 4σ and 10σ and in steps of 10σ afterwards. The yellow circle has a radius of 50'' to illustrate the approximate size of the envelope around A/B sources. The plots show the morphology of the velocity field in the environment of IRAS 16293−2422. A large-scale velocity gradient is observed in the NE−SW direction.