Position−velocity diagram of the HCO⁺J = 3–2 transition of NGC 6334, integrated over the Galactic latitude axis with a cutoff at 3σ = 0.93 K at each velocity channel. The position of the FIR sources are labeled above. Overlaid in contours are the PVDs of the three best-fit models of Sect. 3.3. The contours are set at 50% of the integrated emission which corresponds to the average velocity width of 3.5 km s^-1 of the filament in this figure. The white contour assumes an initial velocity of zero at the edges and the red contour that the filament has already contracted from 7 to 6 pc (both at i = 45°). The model in black contours is defined with a constant velocity value of v = 10 km s^-1 and i = 68°.