Bottom panel: distribution of the number of gas tracers for different cell-mass bins as observed in the simulation (solid lines) vs. a Poisson distribution with parameter λ = ⟨M_cell⟩/m_t (dashed lines, reported in the legend). Top panel: relative difference between the observed mean number of tracer particles and the expected one, λ, as a function of λ. For all cells, the distribution of the number of gas tracers per cell is given by a Poisson distribution with parameter λ.