SIMBAD references

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 v_LSR's between ∼60 and ∼82km/s. Toward SgrB2(N), there is absorption at v_LSR∼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 v_LSR'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 v_LSR∼0km/s component is located close to the galactic center.