Abstract
The 36. 5-GHz (H, He)56α and 22. 4-GHz (H. HE)66α radio recombination lines have been observed in the DR21 with RT22(FIAN). These data combined with the other show that the measured relative abundance y+ of ionized helium appears to increase with the angular beamwidth, ϕA, peaking at ϕA = 2‘–2. 5‘, and then to decrease as ϕA further increases what is more complicated than in previous papers. This behaviour is interpreted as a blister-type model nebula which implies the high actual helium abundance y0 =(26±11)% in the DR21 and its expansion rate from 5km s-1 to 20km s-1 by approaching the observed increasing of the hydrogen radial velocity with the frequency decreasing. Discussion has concerned slightly the explanation possibilities of the high helium abundance too.
Keywords
- Angular Resolution
- Helium Abundance
- Radio Recombination Line
- Measured Relative Abundance
- Explanation Possibility
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Tsivilev, A.P. (1990). The Helium Abundance in the HII Region DR21. In: Gordon, M.A., Sorochenko, R.L. (eds) Radio Recombination Lines: 25 Years of Investigation. Astrophysics and Space Science Library, vol 163. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-0625-9_12
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DOI: https://doi.org/10.1007/978-94-009-0625-9_12
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