Position-position-velocity diagram (PPV) of the stellar and gas motions along the Orion A cloud: (black triangles) APOGEE stellar RVs; (blue and red surfaces) overdensities of APOGEE sources with 5 and 10 stars pc^-2 (km s^-1)^-1; (yellow and green) 0.5 and 2.0 K km s^-1 iso-contours of the ¹²CO emission (Dame et al. 2001) within the area surveyed by APOGEE. The PPV cube is spatially oriented with respect to the Galactic longitude (b; x-axis) and Galactic latitude (l; y-axis) coordinates, both in degrees units. Both gas and stellar velocities (V_LSR; z-axis) refer to the LSR in km s^-1 within the velocity range V_LSR = [−2.0,20.0] km s^-1. The APOGEE sources are projected in the PP (xy) and PV (xz) planes. The spatial densities of [2,10,20,40) stars pc^-2 in the APOGEE sources is also color coded (from red to yellow) in the PP (xy) plane. With the exception of the high stellar velocity dispersion found in clusters like the ONC or NGC 1977, we note how the stellar overdensities are typically clustered in the PPV space and nested within the velocity structure of the gas. The positions of the most important clusters within Orion A are indicated in the plot.