Persson, Sven Eric (1972) Interpretation of the neutral helium triplet spectrum in planetary nebulae. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-08212008-101113
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The theory of the He I triplet spectrum is modified to include the effects of solid particles within the ionized regions of planetary nebulae. New observations of the emission lines [...]5876, 7065, and 10830 are presented for over twenty nebulae, extending the list of objects studied previously by O'Dell. The empirical ratios [...] and [...] are combined with the theory to study the discrepancies between the He I [...] depopulation rates D[...](derived from R[...]), D[...](from R[...]), and D[...] (theoretical). If the presence of dust is neglected, the discrepancies are such that D[...] > D[...] > D[...], in most cases. This is essentially the result found earlier by Capriotti for a smaller sample of objects. Estimates of [...], the [...]10830 dust optical depths which force D[...] = D[...], are derived by accounting for the resonance trapping and dust absorption of the [...]10830 radiation. These estimates are consistent, on an order-of-magnitude basis, with values implied by observed infrared excesses in planetary nebulae, and by simple models of reradiating dust shells.
The important effects of nebular structural features upon the He I triplet spectrum are studied theoretically and observationally. Overall correlations between the apparent [...] depopulation rate discrepancies and nebular parameters are shown to have a connection with a wide range of nebular problems.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Physics, Mathematics and Astronomy|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||28 July 1971|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||09 Sep 2008|
|Last Modified:||26 Dec 2012 02:57|
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