Astronomy and Astrophysics – Astrophysics
Scientific paper
Feb 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995a%26a...294..667h&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 294, no. 3, p. 667-676
Astronomy and Astrophysics
Astrophysics
47
Absorption Spectra, Ammonia, Energy Levels, H Ii Regions, Molecular Clouds, Star Formation, Electron Transitions, Interstellar Matter, Inversions
Scientific paper
Measurements of seven metastable NH3 inversion transitions with (J, K) = (8, 8), (9, 9), (10, 10), (11, 11), (12, 12), (13, 13) and (14, 14) are presented. These lines arise from energy levels between approximately 600 K and approximately 2000 K above the ground state, and are found in absorption toward the H II regions SgrB2(M) and (N) at vLSR's between approximately 60 and approximately 82 km/s. Toward SgrB2(N), there is absorption at vLSR approximately 0 km/s also. The metastable ( J = K) inversion lines are collisionally excited, and an analysis indicates that kinetic temperatures are greater than 600 K. The doublet levels are very subthermally excited, with excitation temperatures less than 10 K. Thus, these lines must arise from the low density, n(H2) less than 5 103/cu cm, extended envelope of SgrB2. In addition, we have measured absorption spectra for the v = 0, J = 1 - 0 transition of SiO and the J = 4 - 3 transition of HC3N toward both sources. The absorptions are seen at vLSR's of approximately 0, and between 60 and 85 km/s, although the HC3N absorption SgrB2(N) is weak and blended with emission. LVG analyses of SiO and the HC3N data are consistent with H2 densities less than 5000/cu cm. Both the NH3 and SiO results are consistent with heating by C shocks. These data strongly indicate that the vLSR approximately 0 km/s component is located close to the galactic center.
Dahmen G.
Henkel Carsten
Huettemeister Susanne
Lemme Claudia
Mauersberger Rainer
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