Radial profile of the rotational excitation temperature of CO v = 2–1 in the disk atmosphere of HD 100546 system. Data points are horizontally shifted slightly for clarity. The excitation temperatures are measured from the population diagrams presented in Fig. 2. The red squares are for an LTE model with fixed line width of 6 km s^-1. The line emissions are optically thick, therefore the column density and the excitation temperature are highly degenerated. The error bars are given not by the fitting error in Fig. 2, but by the total extent of the contour in temperature in the absolute deviation plots in Figs. A.1 and A.2, where the absolute deviation becomes worse by 10% of the best fitting values. The blue triangles are from the fitting of the population diagrams, but with the column density of CO fixed to N_CO = 10²⁰ cm^-2.