Residual CO(1–0) emission in NED01 after subtracting the best-fit disk model computed by BBarolo in the Big region. Left: Map of the blueshifted CO(1–0) residual emission integrated in the range −290 ≲ v[km s⁻¹] ≲ − 200. The blue contours are plotted at 3, 6, 9, 15, and 20σ. The black cross indicates the centre of the best-fit molecular disk. The blue cross indicates the peak of the CO(1–0) residual emission. The residual structure can be enclosed within a box of 8.4″ × 8.4″ (∼3 kpc, see black box overlayed on the map). Centre: Spectrum of the CO(1–0) residual emission extracted from an aperture corresponding to the black box shown in the left panel. The two CO(1–0) peaks are fit with double-Gaussian functions whose parameters are reported in Table 4. Right: Map of the two blueshifted spectral components visible in the central panel, plotted with different colours. The first component (blue contours) is the most blueshifted spectral peaks, integrated within v ∈ [ − 400, −200] km s⁻¹; the second component (in black) corresponds to the secondary peak, integrated between v ∈ [ − 200, 0] km s⁻¹. Contours are plotted at 3, 6, 9, 15, and 20σ.