Statistics – Computation
Scientific paper
Nov 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987a%26as...71..245g&link_type=abstract
Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 71, no. 2, Nov. 1987, p. 245-253.
Statistics
Computation
58
Electron Density (Concentration), Planetary Nebulae, Stellar Evolution, White Dwarf Stars, Computational Chemistry, Stellar Luminosity
Scientific paper
A sample of 30 planetary nebulae with individually determined distances is used to determine nebular parameters such as electron density and ionized mass. The majority of the nebulae studied appear to be ionization bounded. The ionized nebular masses range from <2×10-3 to ⪆5×10-1M_sun;. The volume filling factor is found to be ≡0.75. The distribution of ionized mass as a function of nebular radius and electron density indicates that the observed sample is composed of planetary nebulae with a large spread in intrinsic properties of the central stars and nebulae. The individual distances are compared with distances derived using various statistical distance scales. It appears that such scales in general lead to very uncertain distances in individual cases. The statistical scales that on average show agreement with the 30 individual distances are used to estimate a local planetary nebula birthrate of 2.4±1.3×10-3kpc-3yr-1. It is argued that there is no serious discrepancy with the local birthrate of white dwarfs.
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