Critical metallicity for filament formation, Z_crit, as a function of Stokes number. The initial metallicity and particle scale height are Z_init = 0.01 and H_p,init = 0.015, unless otherwise specified. The colorbar corresponds to the number of particles used in the given simulation and the color of the box edges to the exponent of the size distribution, as shown in the legend. Some of the bar are shifted horizontally for better visibility. The legend on the left-most panel marks the runs, where the particle positions were initialized using different randomization. The horizontal lines cutting through the boxes represent the actual Z_crit values.