Torque acting on discs with different Ṁ and metallicity, with 5 × 10^-8 M_⊙/yr and 0.02 metallicity (top), 1 × 10^-8 M_⊙/yr and 0.03 metallicity (middle) and 5 × 10^-9 M_⊙/yr and 0.05 metallicity (bottom). The black lines encircle the regions of outward migration. The vertical red lines indicate the ice line at 170 K. The migration maps correspond to the disc profiles shown in Fig. 5.