Astronomy and Astrophysics, volume 294, 667-676 (1995/2-3)
A multilevel study of ammonia in star-forming regions. VI. The envelope of Sagittarius B2.
HUETTEMEISTER S., WILSON T.L., MAUERSBERGER R., LEMME C., DAHMEN G. and HENKEL C.
Abstract (from CDS):
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 ∼600K and ∼2000K above the ground state, and are found in absorption toward the HII regions SgrB2(M) and (N) at vLSR's between ∼60 and ∼82km/s. Toward SgrB2(N), there is absorption at vLSR∼0km/s also. The metastable (J=K) inversion lines are collisionally excited, and an analysis indicates that kinetic temperatures are >600K. The doublet levels are very subthermally excited, with excitation temperatures <10K. Thus, these lines must arise from the low density, n(H2)<5 103cm–3, 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 ∼0, and between 60 and 85km/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 <5000cm–3. Both the NH3 and SiO results are consistent with heating by C shocks. These data strongly indicate that the vLSR∼0km/s component is located close to the galactic center.
Galaxy: center - ISM: abundances - ISM: individual objects: Sgr B2 - ISM: molecules - radio lines: ISM
erratum vol.300, p. 636
View the reference in ADS
To bookmark this query, right click on this link: simbad:1995A&A...294..667H and select 'bookmark this link' or equivalent in the popup menu