Sketch illustrating the initial setup. Planetesimals (purple circles) have formed at a single location by streaming instability. They accrete both among themselves as well as from the inward drifting pebbles (blue). The pebble disk and gas disk are marked in light blue and light green, where the gas and pebble scale heights are H_gas and H_peb, respectively. The horizontal black arrow represents the radial width (ηr) of the forming planetesimal ring. Due to dynamical friction, large planetesimals have low eccentricities and inclinations whereas small planetesimals have high velocity dispersions.