Hydrogen recombination lines from the Gum nebula |
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| Authors: | Beate Woermann Michael J Gaylard Robina Otrupcek |
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| Institution: | Department of Physics &Electronics, Rhodes University, Grahamstown 6140, South Africa;Hartebeesthoek Radio Astronomy Observatory, PO Box 443, Krugersdorp 1740, South Africa;Australia Telescope National Facility, PO Box 76, Epping, NSW 2121, Australia |
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| Abstract: | Hydrogen recombination lines in the H156 α and H139 α transitions have been detected at four widely separated positions in the Gum nebula. This confirms that the radio continuum emission seen in parts of the nebula is predominantly bremsstrahlung rather than synchrotron emission.
The derived electron temperatures and emission measures are in the range 4200 to 8500 K and 220 to 470 pc cm?6 respectively. This is consistent with the presence of a low-density, photoionized plasma. The linewidth observed at the position away from the edge of the nebula is significantly larger than those near the edge of the nebula. Together with the negative line velocity observed at this position, this suggests there is systematic expansion of the near side of the nebula. |
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| Keywords: | H ii regions ISM: individual: Gum nebula supernova remnants radio lines: ISM |
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