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The dispersal of dense protostellar material - NH3 hot cores and outflows in Sagittarius B2
Vogel, S. N.; Genzel, R.; Palmer, Patrick
AA(California, University, Berkeley; California Institute of Technology, Pasadena), AB(California, University, Berkeley), AC(Chicago, University, IL)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 316, May 1, 1987, p. 243-257. (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
Ammonia, Gas Flow, Molecular Clouds, Protostars, Star Formation, Astronomical Maps, Centimeter Waves, Emission Spectra, Gas Density, H Ii Regions, Metastable State, Milky Way Galaxy, Optical Thickness
Bibliographic Code:


The authors have observed Sgr B2 in six ammonia transitions using the VLA and have discovered two hot (200K) condensations with diameters of ≡0.2 pc associated with water maser sources; the sources are similar in many respects to the Orion hot core, except they are larger and much more massive. In NH3(N), the northern source, the total NH3 mass is 1000 times higher than in the Orion hot core. Assuming a fractional abundance of 10-5 for ammonia, the total column density and mass are 1025cm-2 and 5000 M_sun;, respectively. In contrast, in the other source, NH3(M), the opacities, densities, and masses are more than two orders of magnitude lower. The hot core emission traces dense gas around newly formed massive stars and is produced during a relatively brief stage after the star begins to heat the surrounding medium and before the dense gas is dispersed by outflow and the emergence of an expanding H II region.

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