a) Contours of constant relative ice surface density peak heights f_Σ,peak (see text for details) as function of turbulence parameter α and solids-to-gas accretion rate ℱ_{s / g}. The gas accretion rate Ṁ_gas is fixed to 10^-8M_⊙yr^-1 and the initial size of the pebbles τ₃ is fixed to 0.03. b) Contours of constant relative ice surface density peak heights (see text for details) as function of the turbulence parameter α and the gas accretion rate Ṁ_gas. The solids-to-gas accretion rate ratio ℱ_{s / g} is fixed to 0.4 and the initial size of the pebbles τ₃ is fixed to 0.03. The cyan lines denote a Toomre parameter (Q_T) of unity at 10 au (1 au); the space below these lines has Q_T< 1 and is gravitationally unstable at 10 au (1 au).