The Molecular Clouds associated with the H II Regions/Candidates between l=207.7 and l=211.7^
Abstract
Using the PMO-13.7 m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous survey of 12CO, 13CO, and C18O J=1-0 emission toward the sky region centered at l=209.7, b=-2.25 with a coverage of 4.0 × 4.5. The majority of the emission in the region comes from the clouds with velocities lying in the range from -3 km s-1 to 55 km s-1, at kinematic distances from 0.5 kpc to 7.0 kpc. The molecular clouds in the region are concentrated into three velocity ranges. The molecular clouds associated with the ten H II regions/candidates are identified and their physical properties are presented. Massive stars are found within Sh2-280, Sh2-282, Sh2-283, and BFS54, and we suggest them to be the candidate excitation sources of the H II regions. The distributions of excitation temperature and line width with the projected distance from the center of H II region/candidate suggest that the majority of the ten H II regions/candidates and their associated molecular gas are three-dimensional structures, rather than two-dimensional structures.