Probability density function of the SPH particles. The blue curve corresponds to the PDF of gas density n and it is proportional to dN/ dlog (n); in other words this curve represents the probability of finding an SPH particle within a certain interval of log (n). The dashed-red curve is the log-normal fit of the PDF of the blue curve in the range 10^-2 to 10². The green curve is the PDF of the sampled population from the original SPH particles while keeping the samples with n> 10² cm^-3. The black crosses trace the combined PDF of the sampled and the original set of the SPH particles. The median density and the dispersion are n_med = 1.3 cm^-3 and σ = 2.1 respectively.