Results of our simulations using parameters δα = 0.05, ζ = 10⁻⁴, and reduced migration speed for planet migration. Panel a shows the reference run with unmodified migration speed. Panel b shows the same run but with twice the migration timescale (e.g. with half of the migration speed), while in panel c the migration timescale is three times resulting in third of the migration speed that displayed in panel a. All simulations are run until the planet reaches 3.7 au (which is chosen arbitrarily). The large black dot and the black line in each panel indicate the planet’s position and its track in the a_pl − m_pl plane.