Space-time diagram showing the evolution of the azimuthally-averaged gas surface density ∑, for the three runs ℳ₃₀₀ (top panel), ℳ₂₀₀ (middle panel), and ℳ₁₀ (bottom panel). The radial extent of all the diagrams range from 0.08 r_p,0 to 3r_p,0, with the planet initially at r_p,0 = 1. The fixed regime is separated from the migrating regime by the vertical black dashed line, and the instantaneous position of the planet is represented by the semi-transparent white line. The estimated inner and outer gap edges in the migrating regime are indicated by the black dotted lines.