SiO (J = 2−1) velocity channel map towards OMC-2 FIR4. White contours are −5 (dashed line), 10, 20, 30, and 40σ levels, with a 1σ = 6.7 × 10⁻⁴ Jy beam⁻¹. The rms was derived for the whole map before the primary beam correction. The white-green crosses represent HOPS-108, HOPS-64, and VLA15 protostars in FIR4 (see Fig. 1 caption for coordinates). The bottom left ellipses represent the synthesised beam, while the white open circle in the bottom right panel marks the primary beam FWHM for the NOEMA observations.