Frame a) the radial density profiles (solid curves and the scale on the left) and the temperature profiles (dashed curves and the scale on the right) for Bonnor-Ebert spheres of 0.2, 0.4, 0.8, and 1.6 M_⊙ (curves from left to right). Frame b) the probability distributions of the column density as the function of the dust temperature for a line-of-sight through the centre of the cloud (solid lines). The curves correspond to the 0.2, 0.4, 0.8, and 1.6 M_⊙ models, from left to right. The dashed lines show the corresponding probability distributions for the total dust mass of the model cloud. All the probability distributions have been normalised to a maximum value of 1.0.