Cumulative flux distribution from vertical escape probability in a ProDiMo model with low UV excess, low gas mass, and low PAH abundance. The top panel of each box shows the vertical optical depth for the line and continuum. The middle panel of each box shows the cumulative flux from the ProDiMo model (black) and best fit slab model (red). The bottom plot of each box shows the CO density distribution in the disk. Outlined with black contours is the region in which radially and vertically between 15 and 85% of the flux originates. The top box is for the ν = 1 − 0 P4 line, the middle box for the ν = 1 − 0 P36 line, the bottom box for the ν = 2 − 1 P4 line.