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Session 107 - The Galactic Center & Bulge.
Display session, Saturday, January 10
Exhibit Hall,

[107.03] Expanding Molecular Shells in Sagittarius B2

R. A. Gaume, J. Martin-Pintado (USNO, OAN), P. de Vicente, T. L. Wilson (OAN, MPIfR)

High resolution (3 arcsecond) images are presented of the (J,K) = (3,3) and (4,4) transitions of ammonia toward the southern portion of the molecular envelope surrounding the Sagittarius B2 region of high mass star formation near the galactic center. These images reveal, for the first time, that the morphology of the Sagittarius B2 molecular envelope is dominated by several shells , incomplete shells (2), and filaments. Several of the shells exhibit ammonia molecular emission at two specific radial velocities; two of the ammonia shells also show a clear systematic velocity gradient indicating expansion. The largest ammonia column densities are found in the intersection of the shells also suggesting expansion. The walls of the shells are warm (>40 K) and contain very compact condensations (< 1 arcsecond), some of which are masering in the ammonia (J,K) = (3,3) transition. We also find several unresolved sources (<1 arcsecond) in the (J,K) = (4,4) transition which show large ammonia densities and temperatures well above 150 K, similar to the Hot Cores found in other regions of massive star formation. These Hot Cores are internally heated and none are associated with centimeter wavelength radio continuum emission, possibly indicating that massive star formation has taken place recently in the molecular envelope of Sgr B2. We discuss the origin of the shells as well as the role of shocks in heating the molecular envelope gas as well as in triggering star formation.

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