Top left panel: continuum emission at 21 cm in Kelvin. Top right and middle panels: H i column density for optically thin assumption and optical depth corrections, respectively. The continuum and H i emission data are based on VGPS, whereas the optical depth correction used in the middle panel is based on the THOR data. The bottom panel shows the H₂ column density from the HiGAL data (Nguyen-Lu’o’ng et al. 2013). In all panels, the black and white/blue contours present the continuum emission at 21 cm (black contours show levels of 10, 30, and 70 K; white/blue contours show levels of 200, 400, 600, and 800 K). The black ellipses in the middle and lower panels have an equivalent radius of r = 80 and 140 pc. Several important objects are marked.