Simultaneous determination of the dust-to-gas ratio and the CO-to-H₂ conversion factor based on method described in Sandstrom et al. (2013). Top-left panel: selected region for the study on the CO(2−1) map. Top-right panel: scatter of the DGR calculated within resolution elements inside the selected area for different X_CO. Bottom-left panel: standard deviation of the DGR as a function of the ration between the CO(2−1) flux and the HI gas surface density. Bottom-right panel: DGR dispersion as a function of X_CO.