Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983a%26a...127..388h&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 127, no. 2, Nov. 1983, p. 388-394.
Astronomy and Astrophysics
Astrophysics
32
Abundance, Astronomical Spectroscopy, Formaldehyde, Gas Density, H Ii Regions, Molecular Clouds, Absorption Spectra, K Lines, Radial Velocity
Scientific paper
The first detections of the interstellar 211 - 212 line of H213CO are presented. The radial velocities of these lines, toward W33 and DR21, differ from those obtained from the 110 - 111 line of H213CO and H212CO. Such differences are probably caused by gradients in the H2 density with radial velocity. The resulting H2 densities are 105.1 cm-3 (W33) and 105.4 (DR21). The H2CO data for Sgr B2 do not give a consistent H2 density. Using the derived H2 densities, corrections for photon trapping are obtained. The corrected (H212CO/H213CO) ratios are ≡100 (W33) and ≡70 (DR21). The result for Sgr B2 is obtained by correcting the measured isotope ratio in the 211 - 212 line, 25±2. The (H212CO/H213CO) ratios are assumed to represent the (12C/13C) ratios; these are combined with double isotope measurements to estimate (16O/18O) and (14N/15N) ratios.
Henkel Carsten
Pauls Thomas
Walmsley Charles Malcolm
Wilson Thomas L.
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