[C II] line-integrated intensity (v_LSR = −10–20 km s⁻¹) from Orion A (16′′ resolution). The red circles delineate the three distinct shells of M 42, M 43, and NGC 1977. The stars indicate the most massive stars within each region: θ¹ Ori C (yellow) in M 42, NU Ori (pink) in M 43, and 42 Orionis (purple) in NGC 1977. Arrows indicate the positions of the four molecular cores OMC1-4 along the Integral-Shaped Filament.