Time evolution of the surface density profile (left panel), with the middle and right panel showing the corresponding ¹³CO J = 3−2 and C¹⁸O J = 3−2 intensity profiles, respectively. The model shown here has M_* = 0.32 M_⊙, α = 10⁻³ and M_disk(t = 0) = 10⁻² M_⊙. The colors, going from red to blue, show different time steps. ¹³CO and C¹⁸O 3–2 intensity profiles for all models can be found in Appendix A.