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Birthrate of PN

Published online by Cambridge University Press:  18 September 2017

D.C.V. Mallik
D.C.V. Mallik*
Affiliation:
Indian Institute of Astrophysics, Bangalore, India

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Recent observations of planetary nebulae have called into question the Shklovsky method of measuring distances. For those planetaries for which independent distance and electron density determinations are available, it is found that the ionized mass and the radius are linearly correlated (Maciel and Pottasch, 1980) and also that the ionized masses increase with decreasing electron density (Pottasch, 1981). These relations imply that the nebulae are optically thick in Ly continuum radiation and the distances based on the Shklovsky method are overestimates. Using an empirically determined mass-radius relationship Maciel and Pottasch have obtained new distances for the nebulae in the catalogue of Milne and Aller (1975). We have used the more complete catalogue of Cahn and Kaler (1971) to obtain distances corrected for possible variations in the ionized mass and have compiled a new list of local planetaries. We obtain a surface density of 15 ± 3 kpc−2 and a planar number density of 44 ± 4 kpc−3.

Type
Abstracts of Contributed Papers
Information
Symposium - International Astronomical Union , Volume 103: Planetary Nebulae , 1983 , pp. 424 - 425
Copyright
Copyright © Reidel 1983 

References

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