BIMA Observations of Complex Molecules in Sgr B2

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Session 30 -- Star Formation, Molecular Clouds and HII Regions
Display presentation, Tuesday, 31, 1994, 9:20-6:30

[30.07] BIMA Observations of Complex Molecules in Sgr B2

D.M.Mehringer, Y.Miao, Y.-J.Kuan, L.E.Snyder (U. of Illinois)

The BIMA mm-wave interferometer has been used to observe several transitions of the complex molecules vinyl cyanide (CH$_2$CHCN), methyl formate (HCOOCH$_3$), and ethyl cyanide (CH$_3$CH$_2$CN) toward the Sgr B2 massive star forming region. In all cases, these species are found to be located toward the northern radio continuum source, Sgr B2(N). The complex molecules are coincident with a center of H$_2$O maser activity as well as a dust core. Three ultracompact H II regions are located within 0.1 pc. The emission from the complex species originates in a region of $<$0.1 pc in size. The column densities of these molecules may be as high as 10$^{16}$ cm$^{-2}$. The association of these molecules with dust supports current chemical models. These models suggest that grain chemistry is responsible for the formation of complex molecular species. The proximity of H$_2$O masers and three ultracompact H II regions suggest that star formation has occurred very recently, perhaps within the last 10$^4$ years. Lines with E$_u$/k$>$100 K are observed, indicating that these molecules are located in very warm material. These complex molecules are not observed in Sgr B2(M), which contains more than 10 ultracompact H II regions. The absence of complex species in Sgr B2(M) suggests that the intense radiation field from the numerous H II regions has destroyed complex species. Sgr B2(M) therefore appears to be more evolved than Sgr B2(N). We acknowledge support from the Laboratory for Astronomical Imaging at the University of Illinois and NSF AST 90-24603.

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