Panel a: first-order moment map of the hyperfine component of the NH₂D line at 110 153.59 MHz. The stars indicate the positions of B1b-N and B1b-S. Blue and red arrows mark the outflow directions. Panel b: zoom around B1b-S of the image shown in a). Panels c, d, and e: are the first-order moment maps of the hyperfine components at the of 110 154.17, 110 153.59, and 110 153.03 MHz in a region of 3″ × 3″ around B1b-S. The same velocity pattern is observed in the three components, which corroborates that the velocity gradient observed in the main component is not an artifact due to self-absorption, but the signature of the pseudo-disk rotation. The green ellipse around the star indicates the beam size, and dark black contours correspond to the continuum emission at 145 GHz reported by Gerin et al. (2015). Continuum contour levels are 20% to 90% in steps of 20% of the peak emission.