Dust temperature of a representative model with parameters of M_dust = 10⁻⁴ M_⊙, R_c = 30 AU, Ψ = 1.15, and H₁₀₀ = 10 AU. For a better representation, we show the quantity $\sqrt{T_{\text{dust\hspace{0.17em}}}}$. The grey solid line refers to the surface of radial optical depth at λ = 0.55 μm being unity, i.e., τ_{radial.55 μm} = 1. This contour marks the disk photosphere where stellar photons are absorbed, and hence plays a crucial role in setting up the temperature structure. The cyan solid line shows the surface of vertical optical depth at λ = 1.3 mm being unity, i.e., τ_{vertical.1.3 mm} = 1. This curve generally reflects the layer above which millimeter continuum emission can reach the observer viewed at a face-on orientation. For comparison, the grey dashed line and cyan dashed line show the same contours for a more massive disk with M_dust = 3 × 10⁻³ M_⊙.