A study of the partially ionized medium in the vicinity of the H II regions NGC 2024 and W3.
Abstract
Summary. Recombination line observations of NGC 2024 and W 3 were made at frequencies of 1 A, 1.6 and 5 GHz. Carbon ncc and n lines are used to locate the ionized carbon relative to the continuum sources and to estimate the electron temperature and density of the C II regions. In both sources two C ii components are required to explain the intensities and radial velocities of the lines as a function of frequency. One component is located at the side of or behind the H ii region; spontaneous line emission from this component is observed at high frequencies. The second component lies in front of the H ii region, and stimulated line emission from this component dominates at low frequencies. The electron temperature and density may be approximately the same in both components; model fits to the observations suggest Te 150 K and ne 25 cm -3. Stimulated emission is also important in the formation of the narrow component of the hydrogen recombination line in NGC 2024. The source of the narrow hydrogen line may not entirely coincide with the spatial extent of the C II region; there is a small velocity difference between the "narrow" hydrogen and the carbon lines. The heavy element recombination line from NGC 2024 is identified with sulfur. The S ii and C II regions are probably not entirely cospatial. Key words: C ii region H i region H II region Radio recombination lines
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 1977
- Bibcode:
- 1977A&A....57..341P
- Keywords:
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- H Ii Regions;
- Hydrogen Ions;
- Interstellar Gas;
- Line Spectra;
- Radiative Recombination;
- Astronomical Models;
- Cosmic Dust;
- Formaldehyde;
- Gas Ionization;
- Astrophysics