Surface-density, Σ, versus temperature corrected mass estimates (using T_d = 30 K for the infrared-bright clumps). The coloured dashed lines in different shades show constant radius (green), n_H number density (red), and escape speed (blue; see Tan et al. 2014). Colours and symbols are the same as in Fig. 8. We mark 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). The dotted line marks the 1 g cm^-3 value of Krumholz & McKee (2008).