Observations of millimeter-wave HCN in four prototype clouds

Details Observations of millimeter-wave HCN in four prototype clouds Observations of millimeter-wave HCN in four prototype clouds

Dec 1975

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1975apj...202..655g&link_type=abstract

Astrophysical Journal, vol. 202, Dec. 15, 1975, pt. 1, p. 655-672.

Astronomy and Astrophysics

Astrophysics

75

Cn Emission, Hydrogen Clouds, Hyperfine Structure, Interstellar Matter, Millimeter Waves, Nebulae, Abundance, Astronomical Models, Brightness Temperature, Doppler Effect, Line Spectra

Scientific paper

High-quality J = 1-0 H(C-12)N and H(C-13)N line profiles at 3.4 mm have been obtained in M17, NGC 2264, Ori A, and NGC 1333. Values for the ratios of the hyperfine-split intensities and the ratio of the integrated intensities of both isotopes are given. Collapsing- or expanding-sphere and turbulent-slab cloud models are used to explain the observed line brightness temperatures, the anomalous ratios of the hyperfine-split components, and the abundances of the isotopes. Doppler overlap and Doppler shifting of hyperfine-split components at 1.7 and 1.1 mm are crucial to the results of radiative transport. Comparison of calculations with the data indicates that the parts of the collapsing or turbulent cloud responsible for observed line widths greater than 1 or 2 km/s cannot be interacting radiatively through these Doppler effects. No such restrictions are important for the expanding sphere. Conditions of high hydrogen density and moderate HCN column density can be found that are consistent with both CS data and the terrestrial ratio of abundances H(C-12)N/H(C-13)N, but not with the observed H(C-13)N hyperfine-split intensity ratios. An isotope ratio smaller than the terrestrial one by a factor of 4 or more is required.

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