Exploration of the large-scale parameter space of the residuals between the data and the models, calculated as the absolute value of model minus data; as data, we used the high spectral resolution data cube of AzTEC/C159, and each model is built with a different pair of v_rot and σ_gas, with the other parameters kept fixed. Left panel: residuals in the inner ring; contours show levels where the residuals exceed 2, 5, and 10 times the minimum value, respectively. Right panel: same, but for the outer ring.