Large-scale CO Multi-line Observations of the S187 HII Region

Abstract

The strong feedback of massive stars profoundly affects the interstellar medium around them, and may trigger the formation of next-generation stars. S187 is a massive star formation region located in the second quadrant of the Milky Way, showing a “Collect and Collapse” triggered star formation pattern. Based on the ${}^{12}\mathrm{CO}$/${}^{13}\mathrm{CO}$/$C^{18}O$ (J=1-0, following J=1-0 is omitted for simplicity) spectra line data from the Milky Way Imaging Scroll Painting (MWISP) survey, the basic properties of the molecular cloud in the S187 region were studied, and the feedback of massive stars to molecular cloud was explored. Using GaussPy+ and clustering algorithm, 32 clouds were identified in this region, and the distances of eight of them were measured by combining the star extinction data of Gaia (Global Astrometric Interferometer for Astrophysics) satellite. The relatively dense gas content traced by ${}^{13}\mathrm{CO}$ and $C^{18}O$ in S187 region is 1-2 orders of magnitude higher than that of molecular clouds in most regions of the second quadrant of the galactic plane. In the S187 region, 243 ${}^{13}\mathrm{CO}$ and 98 $C^{18}O$ clumps were identified, among which 7 ${}^{13}\mathrm{CO}$ and 5 $C^{18}O$ clumps had the potential to form massive stars. The results show that the feedback of massive stars has an obvious effect on the aggregation of molecular cloud around them, which provides conditions for the formation of the next-generation of massive stars.