Physical parameters of an isothermal self-gravitating cylinder (left panel) and sphere (right panel) with fixed p_ext/k = 2 × 10⁴   K   cm^-3 as a function of cloud temperature. Plotted are the cloud diameter (2r_cl, dotted line, scale on left axis), the central density (dashed line, right axis), and the column density through the cloud centre (solid line, right axis). The values given for the size and the density depend on the minimum temperature T_min assumed to be 10   K. For spherical clouds the parameters are shown for all physical solutions including the supercritical ones characterized through an overpressure larger than p_c/p_ext ≈ 14.04. The grey dashed-dotted line in the left hand figure gives the temperature ratio for f_cyl = 0.75.