Surface density vs. mass diagram. Coloured dotted lines in different shades show constant radius (green) and n_H number density (red; cf. Tan et al. 2014). Coloured large circles show clumps (ATLASGAL), while smaller circles show the cores (ALMA 7 m array), colours scaling from blue to red with increasing . We denote two massive cores with M_MDC = 60 M_⊙ (C1-S; Tan et al. 2013) and 55 M_⊙ (CygX-N63; Bontemps et al. 2010). For comparison IRDC clumps (Kainulainen & Tan 2013) and cores are shown (Butler & Tan 2012). Grey arrows show two models: 1) a uniform clump density and 2) a single central object with an r^-2 density profile.