Possible evidence for a variable finestructure constant from QSO absorption lines: motivations, analysis and results
Abstract
An experimental search for variation in the fundamental coupling constants is strongly motivated by modern highenergy physics theories. Comparison of quasar (QSO) absorptionline spectra with laboratory spectra provides a sensitive probe for variability of the finestructure constant, α, over cosmological timescales. We have previously developed and applied a new method providing an orderofmagnitude gain in precision over previous optical astrophysical constraints. Here we extend that work by including new quasar spectra of damped Lymanα absorption systems. We also reanalyse our previous lowerredshift data and confirm our initial results. The constraints on α come from simultaneous fitting of absorption lines of subsets of the following species: Mgi, Mgii, Alii, Aliii, Siii, Crii, Feii, Niii and Znii. We present a detailed description of our methods and results based on an analysis of 49 quasar absorption systems (towards 28 QSOs) covering the redshift range [formmu2]0.5<z<3.5. There is statistical evidence for a smaller α at earlier epochs: [formmu3]Δα/α=(0.72+/0.18)×10^{5}. The new and original samples are independent but separately yield consistent and significant nonzero values of [formmu4]Δα/α. We summarize the results of a thorough investigation of systematic effects published in a companion paper. The value we quote above is the raw value, not corrected for any of these systematic effects. The only significant systematic effects so far identified, if removed from our data, would lead to a more significant deviation of [formmu5]Δα/α from zero.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 November 2001
 DOI:
 10.1046/j.13658711.2001.04840.x
 arXiv:
 arXiv:astroph/0012419
 Bibcode:
 2001MNRAS.327.1208M
 Keywords:

 ATOMIC DATA;
 LINE: PROFILES;
 METHODS: LABORATORY;
 TECHNIQUES: SPECTROSCOPIC;
 QUASARS: ABSORPTION LINES;
 ULTRAVIOLET: GENERAL;
 Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory;
 Nuclear Theory;
 Physics  Atomic Physics
 EPrint:
 17 pages, 3 figures, MNRAS in press, corrected small typos and added an acknowledgment