The Gas-to-Dust Ratio Investigation in the Massive Star-Forming region M17

Abstract

M17 is a well-known massive star-forming region, and its Gas-to-Dust Ratio (GDR) may vary significantly compared to the other areas. The mass of gas can be traced by the $\mathrm{CO}$ emission observed in the \emph{Milky Way Imaging Scroll Painting (MWISP) project}. The dust mass can be traced by analyzing the interstellar extinction magnitude obtained from the \emph{United Kingdom Infrared Telescope (UKIRT)}. We computed the ratio $W(\mathrm{CO})/A_V$: for $A_V\le$ 10 mag, $W{(}^{12}\mathrm{CO})/A_V=(6.27\pm 0.19)$ $\mathrm{K}\cdot km/s\cdot \mathrm{ma}{\mathrm{g}}^{-1}$ and $W{(}^{13}\mathrm{CO})/A_V=(0.75\pm 0.72)$ $\mathrm{K}\cdot km/s\cdot \mathrm{ma}{\mathrm{g}}^{-1}$; whereas for $A_V\ge 10$ mag, $W{(}^{12}\mathrm{CO})/A_V=(15.8\pm 0.06)$ $\mathrm{K}\cdot km/s\cdot \mathrm{ma}{\mathrm{g}}^{-1}$ and $W{(}^{13}\mathrm{CO})/A_V=(3.11\pm 0.25)$ $\mathrm{K}\cdot km/s\cdot \mathrm{ma}{\mathrm{g}}^{-1}$. Then, we converted the $W(\mathrm{CO})/A_V$ into $N(\mathrm{H})/{\mathrm{A}}_{\mathrm{V}}$. Using the WD01 model, we derived the GDR: for $A_V\le$ 10 mag, the GDRs were $118\pm 9$ for ${}^{12}\mathrm{CO}$ and $83\pm 62$ for ${}^{13}\mathrm{CO}$, comparable to those of the Milky Way; however, for $A_V\ge$ 10 mag, the GDRs increased significantly to $296\pm 3$ for ${}^{12}\mathrm{CO}$ and $387\pm 40$ for ${}^{13}\mathrm{CO}$, approximately three times higher than those of the Milky Way. In the discussion, we compared the results of this work with previous studies and provided a detailed discussion of the influence of massive stars and other factors on GDR.

10 pages, 14 figures, 2 tables, Accepted for publication in MNRAS