OMC-2 (upper panels) and LDN 1641N (lower panels) as seen in different surveys. Left panels: ALMA+IRAM-30 m integrated emission of N₂H+ (1−0) at 4.5″. Central panels: CARMA-NRO integrated emission of C¹⁸ O (1−0) at 8″ (Suri et al. 2019). The white dotted line is the footprint of our ALMA+IRAM-30 m observations. Right panels: Herschel+Spitzer dust continuum at 36.2″ (Lombardi et al. 2014). The gold dotted line is the footprint of our ALMA+IRAM-30 m observations, while the white contours represent I(N₂H+) > 5 K km s⁻¹, twice as those in Fig. 1 to highlight the tight correspondence with the high column density material.