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Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra

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Murphy, M. T., Webb, J. K., Flambaum, V. V.·2003·Monthly Notices of the Royal Astronomical Society
DOI 10.1046/j.1365-8711.2003.06970.x
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Abstract

We have previously presented evidence for a varying fine-structure constant, α, in two independent samples of Keck/HIRES quasi-stellar object (QSO) absorption spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2 < zabs < 3.7. The results, with raw statistical errors, indicate a smaller weighted mean α in the absorption clouds: Δα/α= (−0.574 ± 0.102) × 10−5. All three samples separately yield consistent and significant values of Δα/α. The analyses of low-z (i.e. zabs < 1.8) and high-z systems rely on different ions and transitions with very different dependences on α, yet they also give consistent results. We identify an additional source of random error in 22 high-z systems characterized by transitions with a large dynamic range in apparent optical depth. Increasing the statistical errors on Δα/α for these systems gives our fiducial result, a weighted mean Δα/α= (−0.543 ± 0.116) × 10−5, representing 4.7σ evidence for a varying α. Assuming that Δα/α= 0 at zabs= 0, the data marginally prefer a linear increase in α with time rather than a constant offset from the laboratory value: . The two-point correlation function for α is consistent with zero over 0.2–13 Gpc comoving scales and the angular distribution of Δα/α shows no significant dipolar anisotropy. We therefore have no evidence for spatial variations in Δα/α. We extend our previous searches for possible systematic errors, giving detailed analyses of potential kinematic effects, line blending, wavelength miscalibration, spectrograph temperature variations, atmospheric dispersion and isotopic/hyperfine structure effects. The latter two are potentially the most significant. However, overall, known systematic errors do not explain the results. Future many-multiplet analyses of independent QSO spectra from different telescopes and spectrographs will provide a now crucial check on our Keck/HIRES results.

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  • The claim by Webb et al. (1999), Murphy et al. (2003) and King et al. (2012a) that Keck/HIRES data indicated that the fine-structure constant was smaller in the past relaunched interest in fundamental constants.

    “The claim by (Webb et al. 1999;Murphy et al. 2003;King et al. 2012a) that the Keck/HIRES data indicated that the fine structure constant was smaller in the past relaunched the interest in fundamental constants, both from an experimental and theoretical point of view.”

    From Fundamental constants: from measurement to the universe, a window on gravitation and cosmology (2025) · cites this paper as Murphy et al. 2003

  • The analysis of Murphy et al. (2003) relies on 128 absorption spectra, later updated by Murphy et al. (2004) to include 143 absorption systems.

    “The analysis (Murphy et al. 2003) relies on 128 absorption spectra, later updated (Murphy et al. 2004) to include 143 absorption systems.”

    From Fundamental constants: from measurement to the universe, a window on gravitation and cosmology (2025) · cites this paper as Murphy et al. 2003

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3 of the 115 references couldn’t be matched to a known paper.

Research works printed but not linked: 6

  1. Berengut J.C., Dzuba V.A., Flambaum V.V., 2003, Phys. Rev. A, accepted (physics/0305068) · arXiv
  2. Dyson F.J., 1972, in Salam A., Wigner E.P., eds, Aspects of Quantum Theory. Cambridge Univ. Press, Cambridge, p. 213
  3. Dzuba V.A., Flambaum V.V., Murphy M.T., Webb J.K., 2001a, in Karshenboim S.G., Pavone F.S., Bassani G.F., Inguscio M., Hänsch T.W., eds, Lecture Notes in Physics, Vol. 570, The Hydrogen Atom: Precision Physics of Simple Atomic Systems. Springer-Verlag, Berlin, p. 564
  4. Martins C.J.A.P., Melchiorri A., Rocha G., Trotta R., Avelino P.P., Viana P.T.P., 2003, Phys. Rev. Lett., submitted (astro-ph/0302295) · arXiv
  5. Matsubara K., Urabe S., Watanabe M., 2002, in Proc. Asia-Pacific Workshop on Time and Frequency 2002. Daejeon, Korea, p. 290
  6. Vogt S.S. et al., 1994, in Crawford D.L., Craine E.R., eds, Proc. SPIE Vol. 2198, Instrumentation in Astronomy VIII. SPIE, Bellingham, p. 362

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Authors
Murphy, M. T., Webb, J. K., & Flambaum, V. V.
Affiliations
  • University of Cambridge (GB)
  • UNSW Sydney (AU)
Corresponding author
  • Murphy, M. T.
  • Webb, J. K.
ORCID
Venue
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press (OUP)
Published
2003-10
Volume
345
Issue
2
Pages
609-638
ISSN
  • 0035-8711 (ISSN-L)
  • 1365-2966
DOI
10.1046/j.1365-8711.2003.06970.x
OpenAlex
W2153130534
Cited by
514
References
115
Citations by year
2026: 3 · 2025: 8 · 2024: 8 · 2023: 16 · 2022: 9 · 2021: 12 · 2020: 8 · 2019: 11 · 2018: 11 · 2017: 18 · 2016: 17 · 2015: 21 · 2014: 26 · 2013: 23 · 2012: 27
FWCI
24.68
Type
journal article
Language
en
Open access
Locations
  • Monthly Notices of the Royal Astronomical Society (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • Figshare (submittedVersion, cc-by)
  • Swinburne figshare (Swinburne University of Technology) (submittedVersion)
  • arXiv (Cornell University)
  • Swinburne figshare (Swinburne University of Technology)
Funders
  • National Aeronautics and Space Administration
  • W. M. Keck Foundation
  • John Templeton Foundation
  • California Institute of Technology
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Cosmology and Gravitation Theories
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
Keywords
fine-structure constant variation, alpha variation, quasar absorption lines, systematic errors, two-point correlation function

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