Top panel: dust distribution around planets locked in 2:1 resonance at t = 40 Kyr in a Model 1 with Σ₀ = 50 g cm⁻². The black circles give the planets’ positions. Middle panel: histogram of the dust surface density where the planets’ orbital radius is given by a green filled circle. Bottom panel: semi-major axis evolution with time of the outer planet showing a period of stalled migration when the pair of planets are trapped in resonance.