Molecular Clouds in the Galactic Plane from l = [59.°75, 74.°75] and b = [−5.°25, +5.°25]

Abstract In this paper we present the distribution of molecular gas in the Milky Way Galactic plane from l = [59.75, 74.75]° and b = [−5.25, +5.25]°, using the MWISP 12 CO/ 13 CO/C 18 O emission-line data. The molecular gas in this region can be mainly attributed to the Local Spur, Local Arm, Perseus arm, and Outer arm. Statistics of the physical properties of the molecular gas in each arm, such as excitation temperature, optical depth, and column density, are presented. Using the DBSCAN algorithm, we identified 15 extremely distant molecular clouds with kinematic distances of 14.72−17.77 kpc and masses of 363−520 M ⊙ , which we find could be part of the Outer Scutum–Centaurus (OSC) arm identified by Dame & Thaddeus and Sun et al. It is also possible that 12 of these 15 extremely distant molecular clouds constitute an independent structure between the Outer and the OSC arms or a spur. Two Gaussian components exist in the vertical distribution of the molecular gas in the Perseus spiral arm. These two Gaussian components correspond to two giant filaments parallel to the Galactic plane. We find an upward warping of the molecular gas in the Outer spiral arm with a displacement of around 270 pc with respect to the Galactic midplane.