Resumo

PHILLIPS, J. P.. A 1.4 GHZ and 14.7 GHZ analysis of density gradients in galactic planetary nebulae. Rev. mex. astron. astrofis [online]. 2007, vol.43, n.2, pp.303-308. ISSN 0185-1101.

There has been a considerable level of uncertainty as to whether planetary nebulae (PNe) contain radial density gradients. Whilst the work of Taylor et al. (1987) implies that gradients exist in most PNe, that of Siódmiak & Tylenda (2001) suggests precisely the reverse. The work of Phillips (2007) suggests that both of these analyses are suspect, however, and that at least 10 20% of PNe probably do contain gradients. We now extend this latter analysis to include significantly higher frequency fluxes, and use these to undertake a more sensitive analysis of the effects of radial density gradients. We conclude than in excess of 85% of PNe appear to contain gradients, of which 21% are likely to have density exponents β > 1.5, and central cavity sizes which are small (i.e. have radii < 20% of the outer radius of the shell).

Palavras-chave : jets and outflows; planetary nebulae; general.

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