Schematic illustration of the free parameters in the flat Keplerian disk model with a power-law column density and temperature. The grid includes models with with decreasing (α_inner< 0), flat (α_inner = 0) and increasing (α_inner> 0) surface density distributions in the inner 6 AU. The anchor point for the surface density is at 6 AU and for the temperature is at 1 AU. In all the models the cavity radius is at 6 AU.