Three Millimeter Molecular Lines 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

[30.08] Three Millimeter Molecular Lines in SGR B2

Y.-J. Kuan, L.E. Snyder (U. of Illinois)

The giant molecular cloud Sagittarius B2 is known for its active role in massive star formations, chemical evolution, and complex kinematical structure. Studies of molecular transitions from various species in a molecular cloud are essential not only in understanding the chemical evolution of the cloud but also in revealing the physical conditions and structure within the cloud. In this paper, we present the preliminary result of high angular resolution mapping study using 3 millimeter BIMA array in the Sgr B2 region.

We have observed the J = 1-0 transition of C$^{18}$O, J = 9-8 transition of OCS and its isotope OC$^{34}$S, the J$_{K-1K1}$ = 4$_{32}-3_{31}$ and 4$_{31}-3_{30}$ transitions of NH$_{2}$CHO, and the J$_{K-1K1}$ = 4$_{04}-3_{03}$, 5$_{05}-4_{04}$, 4$_{23}-3_{22}$, and 4$_{22}-3_{21}$ transitions of HNCO. C$^{18}$O was found concentrated toward the main HII complex Sgr B2(M) and the region $\sim$15$''$ west of it. The emission from OCS and its isotope mostly originated from the western edge of Sgr B2(M). HNCO, on the other hand, appears to be largely extended and resides in the region surrounding the two massive star forming regions Sgr B2(M) and (N), as indicated by its K$_{-1}$ = 0 emission. The highly excited HNCO emission with non-zero K$_{-1}$ (E$_{u}$/k = 181 K), however, was only detected in the Sgr B2(N) region centered at the dusty hot cores K1-K2-K3; there is a possible bipolar outflow in this region. In addition, the large molecule NH$_{2}$CHO was only detectable in the K1-K2-K3 region, which suggested the production mechanism was mainly grain-surface chemistry (see also Mehringer et al., this meeting).

We acknowledge support from the Laboratory for Astronomical Imaging at the University of Illinois and NSF AST 90-24603.

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