¹²CO emission longitude-latitude map from Dame et al. (2001). The colors represent the ¹²CO velocity-integrated intensity on a logarithmic scale. Solid gray circles indicate the positions of molecular cloud spines identified by Zucker et al. (2021), which trace the central structures of the molecular clouds. Black contours correspond to a CO intensity of 0.7 (in logarithmic units), while blue contours represent different thresholds: 0.75 for Perseus, 0.95 for Taurus, and 0.8 for the Orion regions.