Vol 22, No 4

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

Chun-Xue Li, Hong-Chi Wang, Yue-Hui Ma, Miao-Miao Zhang, Chong Li, Yu-Qing Zheng


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 –104M☉. 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.


Keywords : ISM: molecules – ISM: clouds – ISM: structure – (ISM:) HII regions

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