Maps of the intensity, I_d, of the dust emission at 353 GHz toward the G139 region. Left: observational map from Planck. Middle: best-fit maps reconstructed with the two gas tracers, Hi and CO, before (top) and after (bottom) application of the Gaussian decomposition algorithm ROHSA to each gas tracer. Right: maps of the residuals obtained by subtracting the respective reconstructed maps from the observational Planck map. The color code refers to the absolute residuals, whereas the contour lines follow the relative residuals.