Galactic chemical evolution, AGB stars, and the apparent time variation of the fine structure constant

Grant J. Mathews, T. P. Ashenfelter, Keith A. Olive

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Observations of quasar absorption spectra have suggested a variation of the fine structure constant α. This variation is a generic feature of many unified models of particle physics beyond the standard model, and hence, is a profound result. However, the most statistically significant portion of this sample involves the ratio of Mg to Fe wavelength shifts using the many-multiplet (MM) method. Recent calculations of low-metallicity intermediate-mass AGB stars are particularly important in this regard because they are shown to be copious producers of the heavy Mg isotopes. We have implemented these yields into a chemical evolution model and show that the ensuing isotope distribution of Mg can account for the observed α variation. These observations of quasar absorption spectra can be used to probe the nucleosynthetic history of high redshift (z > 0.5), low metallicity systems. This analysis and other abundances of low metallicity systems strengthen the mounting evidence that early star formation may have been influenced by an enhanced population of intermediate-mass stars. These intermediate-mass stars also affect other elemental and isotopic abundances, particularly CNO cycle elements. We compare our model to independent measurements of the C N, and O elements in Lyman-alpha clouds and show that the scenario we propose is consistent with observations.

Original languageEnglish (US)
Pages (from-to)238-241
Number of pages4
JournalNuclear Physics A
Issue number1-4 SPEC. ISS.
StatePublished - Jul 25 2005

Bibliographical note

Funding Information:
∗Supported by the U.S. Department of Energy under Nuclear Theory Grant DE-FG02-95-ER40934 †supported in part by the U.S. Department of Energy and by NSF grant PHY02-16783 through the Joint Institute for Nuclear Astrophysics physics (JINA). ‡partially supported by DOE grant DE–FG02–94ER–40823.

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