Other
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........46g&link_type=abstract
PhD Dissertation, Calgary Univ. Alberta Canada
Other
Planetary Nebulae, Carbon Monoxide, Ionized Gases, Line Spectra, Photoionization, Ultraviolet Radiation, Stellar Winds, Line Shape, Hydrogen
Scientific paper
The systemic and expansion velocities of the ionized gas of four compact planetary nebulae; CN3-1, M1-78, IC2149, and M1-6 are presented . The results of a survey of atomic hydrogen (HI) absorption in eight compact planetary nebulae (PNe) are presented. Circumnebular HI is found to surround SwStl, M3-35, and Hu2-1. Circumnebular hydrogen emission of IC418 has been mapped. Models of the flux distribution and spectral line shape indicate that the HI may lie in two concentric shells with an inverse-square or inverse-cube power law density gradient. The results of an unsuccessful attempt to map circumnebular HI emission in NGC7027 and BD + 30 deg. 3639 are presented. Observations of carbon monoxide (CO) emission in PNe are presented. Circumnebular J = 2 (yields) 1 CO emission is detected in M1-59, IC5117, M1-16, and NGC6302 Upper limits to J = 2 (yields) 1 CO emission are obtained for nineteen other planetary nebulae. J = 3 (yields) 2 CO emission is observed in M1-78, IC5117, and NGC6302. Upper limits to J = 3 (yield) 2 CO emission are obtained for thirteen nebulae. An unsuccessful attempt to map low-level extended J = 2 (yields) 1 CO emission in NGC7027 is reported. The detectability of CO in PNe is discussed. It is found that the existence of detectable CO is not predicted by any single property of the nebula, although high mass may be a necessary prerequisite. Two major models of PNe the interacting stellar winds model and the photoionized wind model are discussed. It is found that the kinematics of PNe with small ionized radii are adequately represented by the photoionized wind model, but interacting stellar winds are likely to become important in larger nebulae. A spherically-symmetric model of the dissociation and subsequent ionization of the molecular envelope of an evolved star is presented. It is found that the mass of HI observed in IC418 could easily be created by the dissociation of a molecular wind by ultraviolet radiation from the central star.
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