Gas surface density Σ_g, the dust surface density Σ_d and the pebble surface density Σ_p as a function of orbital distance and time in the disc evolution model of Bitsch et al. (2015a), which is used in the planet formation model of Bitsch et al. (2015b). The times are (top to bottom) 10⁴, 10⁵, 10⁶ and 10⁷ yr. The large bump that connects the pebble surface density with the dust surface density indicates the pebble production line r_g. The blue lines correspond to the pebble surface density calculated with a frozen dust distribution outside of 50 AU (Sect. 2.2). The blue arrow indicates the typical pebble surface densities inferred at 10 AU from observations of protoplanetary discs (Williams & Cieza 2011).