Does the fine structure constant vary? A detailed investigation into systematic effects

Abstract

We have previously presented 5.7-sigma evidence for a smaller alpha at redshifts 0.2 < z_abs < 3.7 from a sample of 128 Keck/HIRES quasar absorption systems: da/a = (-0.57 +/- 0.10) x 10^{-5}. A non-zero da/a manifests itself as a distinct pattern of shifts in the measured absorption line wavelengths. The statistical error is now small: we do detect small line shifts in the HIRES data. Whether these shifts are due to systematic errors or due to real variation in alpha is now the central question. Here we summarize the two potentially most important systematic effects: atmospheric dispersion and isotopic abundance evolution. Previously, these have been difficult to quantify/model but here we find that neither of them can explain our results. Furthermore, the HIRES spectra themselves contain no evidence for these effects. Independent measurements of da/a with a different telescope and spectrograph are now crucial if we are to rule out or confirm the present evidence for a variable alpha.

6 pages, 6 EPS figures. Talk presented at JENAM2002 workshop on The Cosmology of Extra Dimensions and Varying Fundamental Constants. To appear in the proceedings

References in corpus (6)

• Further Evidence for Cosmological Evolution of the Fine Structure Constant
• Possible evidence for a variable fine structure constant from QSO absorption lines: motivations, analysis and results
• Possible evidence for a variable fine structure constant from QSO absorption lines: systematic errors
• Galactic Evolution of Silicon Isotopes: Application to Presolar SiC Grains From Meteorites
• The Isotopic Abundances of Magnesium in Stars
• The $\alpha$-dependence of transition frequencies for ions Si II, Cr II, Fe II, Ni II, and Zn II

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