Time evolution of the surface density of gas, dust, and formed planetesimals, with α = 10^−3.4. The sky-blue, blue, and red curves represent the profiles of gas, dust, and planetesimals, respectively. All planetesimals form by streaming instability. The black dashed lines represent the approximation of the planetesimal surface density by Eq. (24) with . The circles and black vertical lines represent the orbital positions of the planet and the snowline, respectively.