Images of the integrated intensity (in K km s^-1) of CO isotopologues (¹²CO, ¹³CO, C¹⁷O, and ¹³C¹⁸O) from the series of representative models (Table 1) with dusty inner disk present (δ_dust = 10^-5). Models with δ_gas = 1,10^-1,10^-2 and 10^-3 are shown. The inclination i = 30° and the black dashed lines show the size of the gap (10 < r < 45 AU). The C¹⁸O images look similar to the C¹⁷O images and thus not shown. 1st row: ¹²CO 3 − 2. 2nd row: ¹³CO 3 − 2. 3rd row: C¹⁷O 3 − 2. 4th row: ¹³C¹⁸O 3 − 2.