A CO study of Sharpless 171 - Evidence for interaction between the H II region and its neighboring molecular cloud

Abstract

Observations of the S171 region were made using the J = 1-0 lines of (CO)-C-12, (CO)-C-13, and (CO)-O-18 emission. The large-scale molecular gas distribution in S171 and its neighborhood has been mapped. Two dense molecular clumps have been revealed near the young star cluster Be 59 in the central region of S171. The mass of these clumps is estimated in total to be 600 M.. A comparison with radio continuum observations shows that the dense gas is contacting with the continuum source. Spectra of (CO)-C-13 and (CO)-O-18 exhibit highly asymmetric shapes, indicating that the dense clumps are suffering dynamic disturbance due to the H II region. The distributed gas component of one of the clumps shows good correspondence with the luminous ridge of the continuum emission. The interpretation is made that ionization fronts generated by the nearby star cluster drive shocks into the molecular clumps. The evolutinary effects of the molecular clumps under the ionization field of massive stars in the region are discussed.