Spacetime diagrams showing the solid surface density Σ_solid as a function of the radial coordinate x and simulation time. The right hand axis shows the mean solid concentration Z = ⟨ Σ_solid ⟩ / ⟨ Σ_total ⟩. The figure shows selected runs with τ_f ≤ 0.03. The top row has runs with standard pressure support (Δ = 0.05) and the bottom row has runs with a reduced pressure support (Δ = 0.025). The surface density is shown by a color scale. Some of the runs form visible filaments. For Δ = 0.05 there is a clear trend where lower τ_f requires higher Z to form filaments. For Δ = 0.025 the behavior is less predictable – while the particle concentration is higher, the low radial drift speed interferes with the streaming instability.