Residual maps (data minus best-fit model, in sigma units) in γ-ray counts in the 0.16–63 GeV band (σ_γ) and in dust optical depth $\left({\sigma }_{{\tau }_{353}}\right)$, obtained when including different sets of gaseous components in the models: without (top) and with (middle) the DNM components in addition to the HI templates. The $N_{{\text{H}}_{\text{DNM}}}$ column-density maps (bottom) extracted from the γ-ray residuals (left) and from dust residuals (right) are shown in the bottom row. The models are derived for an HI at the optically thin case.