Examining the Impact of Early AGB Nucleosynthesis on the Apparent Cosmological Variation in the Fine Structure Constant

Details Examining the Impact of Early AGB Nucleosynthesis on the Apparent Cosmological Variation in the Fine Structure Constant Examining the Impact of Early AGB Nucleosynthesis on the Apparent Cosmological Variation in the Fine Structure Constant

Oct 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aps..dnp.cc001a&link_type=abstract

American Physical Society, Division of Nuclear Physics Meeting, 27-30 October, 2004, Chicago, IL. MEETING ID: DNP04., abstract #

Physics

Nuclear Physics

Scientific paper

Evidence from a large sample of quasar absorption-line spectra in damped Lyman-α systems has shown potential cosmological variation of the fine structure constant α. The most statistically significant portion of this sample involves the comparison of Mg and Fe wavelength shifts using the many-multiplet (MM) method. However, this method is sensitive to the heavy isotopes, especially in Mg. We implement recent yields of intermediate mass (IM) stars, which evolve beyond the CNO cycle, to show that the ensuing isotope distribution of Mg can account for the observed variation in α provided early star-formation was particularly rich in IM stars. During the Asymptotic Giant Branch (AGB) phase of IM stars, heavy Mg isotopes are robustly produced via hot-bottom burning and thermal pulsing in helium burning shell. We incorporate these recently appreciated processes in the galactic chemical evolution models of these damped Lyman-α systems (early galaxies) and delve into the consequences of this chemical evolution alternative to an α variation. We find that this analysis adds to the mounting evidence that the low-metallicity Universe was strongly influenced by IM stars beyond the standard power law distribution of stellar masses. Because these AGB stars have a significant influence on other abundances, especially nitrogen, we use measurements of N, Si Fe, C, and O to constrain our models. In this way, we obtain an alternative explanation of the α variation that is consistent with observations.

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