Histogram of the total column density N(H₂) detected in N₂H⁺ in the different fields explored by the EMERGE Early ALMA Survey (see colours in legend). Three dashed grey lines (at [26, 44, 66] A_V) indicate the column density thresholds used by Hacar et al. (2018) during the analysis of the OMC-1 and OMC-2 regions. The additional six solid black lines (at [20, 40, 60, 80, 100, 120] AV) indicate the new HiFIVe thresholds used in this work in order to cover the wide dynamic range of column densities in our entire sample. The solid red line shows instead the theoretical prediction for high-mass star-formation (Krumholz & McKee 2008).