Steady-state gas density in the belt predicted by our model as a function of r, which is the radial distance to the star. The fiducial model has a = 1, b = 0, R₀ = 100 au, h₀ = 0.05, Ṁ_SW = 1.4 × 10⁻¹⁴ M_⊙/yr, and Ṁ_g = 10⁻³ M_⊕/Myr (see Eq. B.7). Values below R_crit (see Eq. B.8), i.e., above the red line, are not shown. The density beyond the planetesimal width ΔR will mostly scale as r⁻² as the fiducial model (see Appendix G) but it is not represented in the plot.