Comparison between and W_CO maps. Top panel: Mollweide projection of our map. The dark blue color indicates regions with . Bottom panel: W_CO map from Dame et al. (2001). Our map was constructed by calculating A_V(H₂), using E(B − V) and N_H I data, and then converting to using the relation given in Eq. (7). The map shows several relatively large angular scale structures. As these are CO-dark H₂ regions, they are undetectable in the W_CO map. (Sect. 5.2). In both maps, longitude increases to the left from the central (vertical) line at ℓ = 0°, the grid spacing, shown by the white solid lines, is 30°, the angular resolution is 16′, and the HEALPix parameter NSIDE = 1024.