Left: column density on a 0.3 × 0.3 × 0.25 pc³ box around a globule in the Mach 4 simulation. Right: mass-weighted histogram of the line-of-sight velocity in the same box (similar to optically thin observational line spectra). Each spectrum is made on a square of 0.05 × 0.05 pc² drawn on the column density map. The spectra are drawn between − 6 and 6 km s^-1 in 80 bins (horizontal axis) and for mass between 10⁴ and 1 solar masses (vertical axis in log scale). All the spectra are red-shifted by a velocity of +4 km s^-1.