Mass (in units of solar mass M_⊙) versus radius (in units of pc) of the molecular clumps in our sample compared with the static Bonnor-Ebert sphere. The top curve (e.g. Kauffmann & Pilltai 2010) represents the mass–radius threshold for forming massive stars. The other curves are the critical masses that can be supported for clumps of specified temperatures and sizes. T_eq = 51 K corresponds to a turbulent linewidth of ~1 km s^-1 (FWHM), and 165 K corresponds to a linewidth of ~1.8 km s^-1.