Upper two panels and lower panels: same as Figs. 5 and 4, respectively, but with a heavier gas disc, Disc A′. The yellow and blue plots in the upper two panels represent the profiles with the normal and half migration speed, respectively, with Ṁ_peb = 10⁻³ M_E yr⁻¹. The orange plots indicate the profile with Ṁ_peb = 10⁻⁴ M_E yr⁻¹ and the normal migration speed. The light blue and purple curves in the middle panel represent the profiles with Ṁ_peb = 10⁻⁴ and 10⁻⁵ M_E yr⁻¹, respectively, with the normal migration speed. Lower panel: Ṁ_peb = 10⁻³ M_E yr⁻¹.