THE CURIOUS CONUNDRUM REGARDING SULFUR ABUNDANCES IN PLANETARY NEBULAE

Sulfur abundances derived from optical emission line measurements and ionization correction factors (ICFs) in planetary nebulae are systematically lower than expected for the objects' metallicities. We have carefully considered a large range of explanations for this "sulfur anomaly,"...

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Bibliographic Details
Published in:The Astrophysical journal 2012-04, Vol.749 (1), p.1-15
Main Authors: HENRY, R. B. C, SPECK, Angela, KARAKAS, Amanda I, FERLAND, Gary J, MAGUIRE, Mason
Format: Article
Language:English
Subjects:
ABUNDANCE
Anomalies
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Asymptotic giant branch stars
Balancing
DUSTS
Earth, ocean, space
Emission
Exact sciences and technology
IONIZATION
Metallicity
PHOTON EMISSION
PLANETARY NEBULAE
RECOMBINATION
Sequestering
STAR EVOLUTION
STARS
Sulfur
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Summary:Sulfur abundances derived from optical emission line measurements and ionization correction factors (ICFs) in planetary nebulae are systematically lower than expected for the objects' metallicities. We have carefully considered a large range of explanations for this "sulfur anomaly," including: (1) correlations between the size of the sulfur deficit and numerous nebular and central star properties, (2) ICFs which undercorrect for unobserved ions, (3) effects of dielectronic recombination on the sulfur ionization balance, (4) sequestering of S into dust and/or molecules, and (5) excessive destruction of S or production of O by asymptotic giant branch stars. It appears that all but the second scenario can be ruled out. However, we find evidence that the sulfur deficit is generally reduced but not eliminated when S super(+3) abundances determined directly from IR measurements are used in place of the customary sulfur ICF. We tentatively conclude that the sulfur anomaly is caused by the inability of commonly used ICFs to properly correct for populations of ionization stages higher than S super(+2).
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/749/1/61