منابع مشابه
The iron abundance in four planetary nebulae
We have observed the high excitation planetary nebulae NGC 7027, NGC 6543 and the low excitation planetaries Hu 2-1 and Cn 3-1 in the optical & near IR with the aim to contribute accurate measurements of their gaseous iron abundances. Use was made of multi-level atomic models of iron ions to interpret the observed forbidden lines of various iron ions. The resulting total abundances are: N(Fe)/N...
متن کاملPlanetary Nebulae: Abundances and Abundance Gradients
In this work, a review is given of some recent results and problems involved in the determination of chemical abundances of galactic planetary nebulae, particularly regarding disk and bulge objects.
متن کاملThe O Ii Recombination Line Abundance Problem in Planetary Nebulae
Presentamos observaciones de ĺıneas de recombinación de O II en diez nebulosas planetarias brillantes, y mediciones de O II y [O III] con resolución espacial en NGC 6720. Esto es con el fin de estudiar la discrepancia entre las abundancias calculadas con ĺıneas de recombinación de O II y aquellas derivadas de ĺıneas de excitación colisional de [O III]. Observamos una gran variación en la discre...
متن کاملAbundance gradients in the outer galactic disk from planetary nebulae
Radial abundance gradients of the element ratios O/H, Ne/H, S/H, and Ar/H are determined on the basis of a sample of disk planetary nebulae. The behaviour of the gradients at large distances from the galactic centre, R > R0 = 7.6 kpc, is emphasized. It is concluded that the derived gradients are consistent with an approximately constant slope in the inner parts of the Galaxy, and some flattenin...
متن کاملPlanetary Nebulae as a Chemical Evolution Tool: Abundance Gradients
We have studied the time variation of the radial abundance gradients using samples of planetary nebulae, open clusters, cepheids and other young objects. Based on the analysis of O/H and S/H abundances for planetary nebulae and metallicities of the remaining objects, we concluded that the gradients have been flattening out in the last 8 Gyr with an average rate of the order of 0.005 – 0.010 dex...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 2000
ISSN: 0074-1809
DOI: 10.1017/s0074180900167099