On The Electron Temperature of Extended, Low Density HII Regions

  • A. Pedlar
  • R. D. Davies
Part of the Astrophysics and Space Science Library book series (ASSL, volume 80)


Radio recombination lines are probably the most reliable method of determining the electron temperatures of low density HII regions. In high density objects with high emission measures, considerable error can be introduced by the enhancement of the line intensity by stimulated emission (Seaton 1974). Such effects are small in low emission measure objects (E<104 pc cm-6). This has been demonstrated by observations of low frequency lines in the cases of W1, W16, W35 and W80, where no strong evidence for enhancement was found in a comparison of 220α and 166α lines (Pedlar & Davies 1972, Pedlar 1980). This implies that the 166α measurements lead to an electron temperature which is not seriously in error.


Electron Temperature Emission Measure Galactic Centre Average Electron Galactocentric Distance 
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Copyright information

© D. Reidel Publishing Company 1980

Authors and Affiliations

  • A. Pedlar
    • 1
  • R. D. Davies
    • 1
  1. 1.Nuffield Radio Astronomy Laboratories Jodrell BankMacclesfield, CheshireUK

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