Determination of average line of sight motions for Orion A. Top: PV-diagram (v_LSR vs l) for gas and YSOs in Orion A. The gas velocities (gray small dots) were extracted as the 1st Moment of the ¹²CO(2-1) map from Nishimura et al. (2015). Only pixels within a smoothed column-density contour of A_K > 0.5 mag were used to avoid contamination by background emission. The black dots show the selected YSO sample that satisfies the Gaia and APOGEE-2 quality criteria. The averages per region for YSOs and gas are shown with orange and blue diamonds, respectively, with the error bars representing the velocity dispersion per region (see also Fig. E.1). The l-positions of these symbols were shifted from mid-bin-positions for better visibility. Bottom: velocity map as derived from the CO measurements per pixel. The pixel values are given in v_LSR, as shown by the color-scale, and were used for the PV-diagram (top panel). The nine subregions are labeled within the bins at the top of the frame, and their average l, b positions are shown as gray circles, which are used for the traceback. The bins enclosing NGC 1977 and NGC 1981 were excluded (gray shaded area, top panel), since the gas and YSOs appear decoupled.