The color map shows the dust temperature in polar (r, θ) coordinates for a 10 Å grain of silicate. The white lines in the figure represent the parabolic flow lines with various starting/launch radii on the accretion disk, r₀. The brown line demarcates the region where dust temperatures are lower than the sublimation temperature, taken to be ∼2000 K. Hence, the region on the left side of the line is the sublimation zone, which is free of dust grains.