Molecular Clouds Associated with {H \small{II}} regions and Candidates within l = 106.65${}^{\circ }$ to 109.50${}^{\circ }$ and b = $-$1.85${}^{\circ }$ to 0.95${}^{\circ }$

Abstract

We present a large-scale simultaneous survey of the CO isotopologues (${}^{12}\mathrm{CO}$, ${}^{13}\mathrm{CO}$, and $\mathrm{C}{}^{18}\mathrm{O}$) J = 1 $-$ 0 line emission toward the Galactic plane region of l = 106.65${}^{\circ }$ to 109.50${}^{\circ }$ and b = $-$1.85${}^{\circ }$ to 0.95${}^{\circ }$ 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] $\mathrm{km}{\mathrm{s}}^{-1}$. The gas in the region can be divided into four clouds, with mass in the range of $\sim$10${}^3$ to 10${}^4$\,${M_{\sun}}$. We have identified 25 filaments based on the ${}^{13}\mathrm{CO}$ 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 $M_{\odot }\mathrm{p}{\mathrm{c}}^{-1}$, 1.01 $\mathrm{km}{\mathrm{s}}^{-1}$, 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 \small {II}} regions or candidates have previously been found in the region and we investigate the relationships between these {H \small {II}} regions/candidates and surrounding molecular clouds in detail. Using morphology similarity and radial velocity consistency between {H \small {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 \small {II}} regions/candidates are associated with their surrounding molecular clouds. In the case of the {H \small {II}} region of S142, the energy of the {H \small {II}} region is sufficient to maintain the turbulence in the surrounding molecular gas.

41 pages, 25 figures

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