VLT/UVES constraints on the cosmological variability of the fine-structure constant
Department of Theoretical Astrophysics, Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia e-mail: email@example.com
2 Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
3 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
Accepted: 12 January 2005
We propose a new methodology for probing the cosmological variability of α from pairs of lines (SIDAM, single ion differential α measurement) observed in individual exposures from a high resolution spectrograph. By this we avoid the influence of the spectral shifts due to ionization inhomogeneities in the absorbers; and non-zero offsets between different exposures. Applied to the lines of the metal absorption line system at zabs = 1.839 in the spectrum of Q 1101–264 obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT), SIDAM provides = . The zabs = 1.15 system toward HE 0515–4414 has been re-analyzed by this method thus obtaining for the combined sample = . These values are shifted with respect to the Keck/HIRES mean = (Murphy et al. 2004) at very high confidence level (95%). The fundamental photon noise limitation in the measurement with the VLT/UVES is discussed to figure the prospects for future observations. It is suggested that with a spectrograph of ~10 times the UVES dispersion coupled to a 100 m class telescope the present Oklo level ( ≥ 4.5 10-8) can be achieved along cosmological distances with differential measurements of .
Key words: cosmology: observations / line: profiles / galaxies: quasars: absorption lines / galaxies: quasars: individual: Q 1101–264, HE 0515–4414
© ESO, 2005