Non-metastable ammonia absorption toward compact H II regions

Details Non-metastable ammonia absorption toward compact H II regions Non-metastable ammonia absorption toward compact H II regions

Nov 1983

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983a%26a...127l..19w&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 127, no. 2, Nov. 1983, p. L19-L22.

Astronomy and Astrophysics

Astrophysics

44

Absorption Spectra, Ammonia, H Ii Regions, Line Spectra, Molecular Absorption, Molecular Clouds, Hyperfine Structure, Interstellar Matter, Optical Thickness, Stellar Evolution

Scientific paper

Absorption from the non-metastable (J,K) = (2,1) line of NH3 has been detected toward the compact H II regions in W31 and NGC 7538; the relative intensities are consistent with LTE. Measurements of metastable (J = K) absorption lines for these sources show total optical depths of >10, among the largest found so far in NH3 in the interstellar medium. From ratios of the optical depths of metastable lines, rotational temperatures are ≡120K to ≡170K; model calculations show that kinetic temperatures are somewhat larger. These temperatures and optical depths are used to calculate a total NH3 column density of ≡1018 cm-2. The NH3 density is ≡10 cm-3. The authors estimate that the (NH3/H2) ratio is 10-4 - 10-5, which is >100 times larger than typical for molecular clouds.

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