Molecular Clouds Associated with H ii Regions and Candidates within l = 106.°65 to 109.°50 and b = −1.°85 to 0.°95

Abstract

We present a large-scale simultaneous survey of the CO isotopologues (12CO, 13CO, and C18O) J = 1–0 line emission toward the Galactic plane region of l = 106.°65 to 109.°50 and b = −1.°85 to 0.°95 using the Purple Mountain Observatory 13.7 m millimeter-wavelength telescope. Except for the molecular gas in the solar neighborhood, the emission from the molecular gas in this region is concentrated in the velocity range of [−60, −35] km s−1. The gas in the region can be divided into four clouds, with mass in the range of ∼103–104 M ☉. We have identified 25 filaments based on the 13CO data. The median excitation temperature, length, line mass, line width, and virial parameter of the filaments are 10.89 K, 8.49 pc, 146.11 M ⊙ pc−1, 1.01 km s−1, and 3.14, respectively. Among these filaments, eight have virial parameters of less than 2, suggesting that they are gravitationally bound and can lead to star formation. Nineteen H ii regions or candidates have previously been found in the region and we investigate the relationships between these H ii regions/candidates and surrounding molecular clouds in detail. Using morphology similarity and radial velocity consistency between H ii regions/candidates and molecular clouds as evidence for association, and raised temperature and velocity broadening as signatures of interaction, we propose that 12 H ii regions/candidates are associated with their surrounding molecular clouds. In the case of the H ii region of S142, the energy of the H ii region is sufficient to maintain the turbulence in the surrounding molecular gas.