Astron. Astrophys. 358, 1049-1057 (2000)

The intrinsic structures of circular and elliptical planetary nebulae

J.P. Phillips

Instituto de Astronomia y Meteorologia, Av. Vallarta No. 2602, Col. Arcos Vallarta, C.P. 44130 Guadalajara, Jalisco, Mexico

Received 14 December 1999 / Accepted 23 March 2000

Abstract

Planetary nebula axial ratios have been used to investigate the intrinsic structures of sources having elliptical or circular morphologies, using methods previously applied to elliptical galaxies. The results appear to indicate that most such nebulae have intrinsic axial ratios in the range 0.920.75, and that gradients of surface brightness with axial ratio are most consistent with oblate shell structures. It remains possible however, given the uncertainties in the analysis, that many circular or ellipsoidal planetary nebulae also have prolate configurations. Whilst there may be evidence for an evolution of axial ratio with nebular radius, there appears to be little variation with Galactic latitude. This would suggest that nebular asphericities are not, in the main, dependent upon interaction with the interstellar medium, and that the variation of axial ratio with progenitor mass is also quite low.

Key words: ISM: planetary nebulae: general ISM: structure

Send offprint requests to: J.P. Phillips

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Contents

• 1. Introduction
• 2. Observational data set
  • 2.1. Optical data base
  • 2.2. Radio data base
• 3. Intrinsic distribution of axial ratios
• 4. Variation of surface brightness with axial ratio
• 5. Evolution in ellipticities
• 6. Influence of the interstellar medium and progenitor masses upon nebular ellipticities
• 7. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000
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