Mass-radius relationship of cores. The red star, green circle, and blue square indicate protostellar, prestellar, and unbound starless cores, respectively. The pink line shows that the mass-radius relationship for all the cores can be well fit with a power law: M ∝ R^1.85. The gray shaded region indicates that high-mass stars cannot form (Kauffmann et al. 2010). The green line presents surface densities of 116 M_⊙ pc². The red linepresents the surface density of the critical Bonnor-Ebert sphere.