Torque acting on discs with different Ṁ, with 5 × 10^-8 M_⊙/yr (top), 1 × 10^-8 M_⊙/yr (middle) and 5 × 10^-9 M_⊙/yr (bottom) for the applied Paardekooper et al. (2011) formula. The black lines encircle the regions of outward migration for the Paardekooper et al. (2011) formula. The vertical solid yellow lines mark the outer edge of the zero-migration region for the unsaturated torques (Paardekooper et al. 2010), while the dashed-yellow line marks the inner edge of the zero migration region of the unsaturated torques. The vertical red lines indicate the ice line at 170 K.