Left: weighted histogram of the number of prestellar and protostellar cores per bin (left y-axis) and lifetime of the (massive) prestellar phase (right y-axis) for each bin (points). Prestellar cores are shown in blue bars, protostellar cores in red, and free-free sources in yellow. The bins are constructed using the average mass adopted in Table A.1 (also available at the CDS). Protostellar cores masses were corrected assuming a decrease in the core mass envelope over time (see Sect. 7.4), with a constant accretion and a core to star efficiency ϵ_cse of 50%. Prestellar lifetimes are presented as blue points for the average mass adopted, black and brown points for the lower and upper mass limits. The magenta dashed line represents the threshold in mass of the protostar to start ionizing its envelope. The upper x-axis represents the final stellar mass assuming a core to star efficiency ϵ_cse of 50%. Right: same histogram with the mean prestellar lifetime in cyan stars extracted from the three hypotheses in the left panel. The cyan dashed lines represent the one-sigma dispersion.