Outflow speed as a function of dimensionless planetary mass. The cross symbols are the maximum value of the outflow speed at the Bondi (for m001, m005, m01, m05) or Hill radius (for m1, m2) on the midplane of the disc obtained from our simulations at t = t_end. The blue and orange solid lines correspond to the analytical solution of the outflow speed derived from Eqs. (17) and (18), which are divided at the point where the size of the Bondi radius of the planet exceeds the size of the Hill radius (see Sect. 3.3 for details). Each black lineshows the changes of the relative velocity of the small particles for each Stokes number, St = 10⁻³ (dashed-dotted line), 10⁻² (dotted line), and 10⁻¹ (dashed line) derived from Eqs. (24) and (25); (see Sect. 4.3 for details).