Testing different methods to calculate CO line ratios and the effect of masking. We show the relative difference between the true and measured line ratio ΔLR/LR_true with ΔLR=LR_true - LR_measured. We estimate the measured line ratio LR_measured per three different methods (sum: sum(M)/sum(CO) in blue, mean: mean(M/CO) in orange, median: median(mock/CO) in purple) with M and CO indicating the intensity of the mock and CO data, respectively. We further test the impact of different masking on the moment maps: Utilizing all pixels in the FoV (squares), only pixels where CO is significantly detected (> 3σ, circle), and only pixels where N₂H⁺ is significantly detected (> 3σ, pentagons). The color gradient indicates the S/N of the data cube (measured via LR_true), with darker color being LR_true = 0.024 and the faintest color LR_true = 0.0036. Points of the same color (albeit different gradient) belong to the same method.