Position-velocity cut of the CO(2−1) emission in false colours and black contours performed along the direction of the collimated jet identified by Br1 and Bb1 CO knots in Fig. 2 (along the cyan solid line in Figs. 1, 2, PA = 116°). Labels are the same as in Fig. 2. Dashed vertical white lines mark the positions of VLA1623A and VLA1623B, while the dashed horizontal white line indicates the ambient systemic velocity of 3.6 km s^-1, derived by Narayanan & Logan (2006) from N₂H⁺ observations taken with the Five College Radio Astronomy Observatory (FCRAO; see also Yu & Chernin 1997). Dotted black lines connect the corresponding blue- and red-shifted knots associated with the possibly new fast and collimated jet emission detected with ALMA and labelled in Fig. 2. Both pairs of corresponding knots seem to be associated with B rather than with A.