a) Histograms of the bolometric luminosity extrapolated from the monochromatic luminosity at 22 μm from Mottram et al. (2011), b) the mass, and c) the surface density for the whole sample. The dotted line in panel b) shows the mass limit of 650 M_⊙. The dashed line in panel c) show the theoretical value of 1 g cm^-2 from (Krumholz & McKee 2008). The colour scheme is the same as in Fig. 2 and is indicated in the legend of panel a).