De-projection analysis of the PV diagram of the OB cluster forming region G10.6-0.4 (ψ = 25°). To perform the de-projection, we evaluated the absolute velocity field based on the enclosed mass. We adopt the value of centrally embedded stellar mass to be 175 M_⊙ (Sollins & Ho 2005). The velocity vectors are twisted from pure rotational motions toward the center by 25°. Left: PV diagram of the CH₃OH 5_0,5–4_0,4 E transition in G10.6-0.4 (see also Liu et al. 2011). Contour levels are 0.36 Jy beam^-1× [1, 2, 3, 4, 5, 6, 7]. Regions in this PV diagram that cannot be explained with the velocity field model are masked with red dots. Right: 2 dimensional image of the de-projected structures. Dashed lines are the iso line-of-sight velocity contours, start from −5.0 km s^-1, separated by ±0.5 km s^-1. The de-projected image shows elongated large scale structure (≳0.5 pc) from bottom left to top right. More complicated structures are seen within the central ~0.15 pc radius.