Distribution and Properties of Molecular Gas Toward the Monoceros OB1 Region

Abstract

We perform a comprehensive CO study toward the Monoceros OB1 (Mon OB1) region based on the MWISP survey at an angular resolution of about $50^{\prime \prime }$. The high-sensitivity data, together with the high dynamic range, shows that molecular gas in the $8^{\circ }\times 4^{\circ }$ region displays complicated hierarchical structures and various morphology (e.g., filamentary, cavity-like, shell-like, and other irregular structures). Based on Gaussian decomposition and clustering for ${}^{13}\mathrm{CO}$ data, a total of 263 ${}^{13}\mathrm{CO}$ structures are identified in the whole region, and 88% of raw data flux is recovered. The dense gas with relatively high column density from the integrated CO emission is mainly concentrated in the region where multiple ${}^{13}\mathrm{CO}$ structures are overlapped. Combining the results of 32 large ${}^{13}\mathrm{CO}$ structures with distances from Gaia DR3, we estimate an average distance of $729_{-45}^{+45}\mathrm{pc}$ for the GMC complex. The total mass of the GMC Complex traced by ${}^{12}\mathrm{CO}$, ${}^{13}\mathrm{CO}$, and ${\mathrm{C}}^{18}\mathrm{O}$ are $1.1\times 10^5{M}_{\odot }$, $4.3\times 10^4{M}_{\odot }$, and $8.4\times 10^3{M}_{\odot }$, respectively. The dense gas fraction shows a clear difference between Mon OB1 GMC East (12.4%) and Mon OB1 GMC West (3.3%). Our results show that the dense gas environment is closely linked to the nearby star-forming regions. On the other hand, star-forming activities have a great influence on the physical properties of the surrounding molecular gas (e.g., greater velocity dispersion, higher temperatures, and more complex velocity structures, etc.). We also discuss the distribution/kinematics of molecular gas associated with nearby star-forming activities.

28 pages, 17 figures, match to the version of APJ, 966, 202. The dataset has been released on https://doi.org/10.57760/sciencedb.17451