The Molecular Clouds associated with the H II Regions/Candidates between $l=207.7^{\circ }$ and $l=211.7^{\circ }$

Abstract

Using the PMO-13.7 m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous survey of ${}^{12}$CO, ${}^{13}$CO, and C${}^{18}$O $J=1-0$ emission toward the sky region centered at $l$=$209.7^{\circ }$, $b$=$-$2.25${}^{\circ }$ with a coverage of $4.0^{\circ }\times 4.5^{\circ }$. 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.

28 pages, 30 figures