منابع مشابه
The temperature structure of dusty planetary nebulae
We have analyzed the effects of photoelectric heating by dust grains in photoionization models of planetary nebulae. We have shown that this process is particularly important if planetary nebulae contain a population of small grains. The presence of such grains would solve a number of problems that have found no satisfactory solution so far: i) the thermal energy deficit in some objects inferre...
متن کاملPlanetary Nebulae
Planetary nebulae (PNe) can be used to trace intermediate and old stellar populations in galaxies and the intracluster medium out to approximately 20 Mpc. PNe can be easily identified with narrow-band surveys, and their chemical abundances and radial velocities can be measured with multi-slit or multi-fiber spectrographs. We briefly review what has been accomplished to date, and include tables ...
متن کاملFluorine Abundances in Planetary Nebulae
We have determined fluorine abundances from the [F II] λ4789 and [F IV] λ4060 nebular emission lines for a sample of planetary nebulae (PNe). Our results show that fluorine is generally overabundant in PNe, thus providing new evidence for the synthesis of fluorine in asymptotic giant branch (AGB) stars. [F/O] is found to be positively correlated with the C/O abundance ratio, in agreement with t...
متن کاملCO Isotopes in Planetary Nebulae
Standard stellar evolution theory is inconsistent with the observed isotopic carbon ratio, C/C, in evolved stars. This theory is also inconsistent with the He/H abundance ratios observed in Galactic H II regions, when combined with chemical evolution theory. These discrepancies have been attributed to an extra, non-standard mixing which further processes material during the RGB and should lower...
متن کاملIntracluster Planetary Nebulae
We review the progress of research on intracluster planetary nebulae (IPN). In the past five years, hundreds of IPN candidates have been detected in the Virgo and Fornax galaxy clusters and searches are also underway in poorer galaxy groups. From the observations to date, and applying the known properties of extragalactic planetary nebulae, the intracluster light in Virgo and Fornax: 1) is sign...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1974
ISSN: 0074-1809
DOI: 10.1017/s0074180900026759