Top panel: distribution of stellar surface densities predicted by our model for a clump of mass M₀ ≃ 10⁴   M_⊙, radius R ≃ 6   pc, and star formation efficiency per free-fall time ϵ_ff = 0.1 (clump density index p₀ and time t since star formation onset are given in the key). Bottom panel: two p₀ = 1.7 models are shown at time t = 1 Myr and t = 2 Myr for the same molecular clump as above (lines with open symbols). The dotted and dash-dotted (black) lines depict two Gaussians fitting their low-density regime. The solid (red) line is the Gaussian given by Bressert et al. (2010) to describe the observed local surface density distribution of YSOs in the solar neighbourhood. Mean and standard deviation of all three Gaussians are given in brackets.