Typical velocity-integrated intensity maps of CO(2–1) for diffuse (left), moderate (middle), and compact structures (right) of Galactic edge clouds (T_mb scale; color bar in units of K km s⁻¹). The black circles in the center of each map represent the CO(1–0) emission peaks identified from the Delingha 13.7 m telescope, and their size corresponds to the telescope beam size of ∼ 52^′′. The gray filled circles in the lower-left corner show the beam size of CO(2–1) observed with the IRAM 30 m telescope.