EDP Sciences
Free Access
Volume 434, Number 3, May II 2005
Page(s) 827 - 838
Section Cosmology (including clusters of galaxies)
DOI https://doi.org/10.1051/0004-6361:20041827
Published online 18 April 2005

A&A 434, 827-838 (2005)
DOI: 10.1051/0004-6361:20041827

VLT/UVES constraints on the cosmological variability of the fine-structure constant

S. A. Levshakov1, M. Centurión2, P. Molaro2 and S. D'Odorico3

1  Department of Theoretical Astrophysics, Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
    e-mail: lev@astro.ioffe.rssi.ru
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

(Received 10 August 2004 / Accepted 12 January 2005 )

We propose a new methodology for probing the cosmological variability of $\alpha$ from pairs of $\ion{Fe}{ii}$ lines (SIDAM, single ion differential $\alpha$ measurement) observed in individual exposures from a high resolution spectrograph. By this we avoid the influence of the spectral shifts due to (i) ionization inhomogeneities in the absorbers; and (ii) non-zero offsets between different exposures. Applied to the $\ion{Fe}{ii}$ lines of the metal absorption line system at $z_{\rm abs}$ = 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 $\Delta\alpha/\alpha$ = $(2.4\pm3.8_{\rm stat})\times10^{-6}$. The $z_{\rm abs}$ = 1.15 $\ion{Fe}{ii}$ system toward HE 0515-4414 has been re-analyzed by this method thus obtaining for the combined sample $\Delta\alpha/\alpha$ = $(0.4\pm1.5_{\rm stat})\times10^{-6}$. These values are shifted with respect to the Keck/HIRES mean $\Delta\alpha/\alpha$ = $(-5.7\,\pm\,1.1_{\rm stat})\times10^{-6}$ (Murphy et al. 2004) at very high confidence level (95%). The fundamental photon noise limitation in the $\Delta\alpha/\alpha$ 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 ( $\Delta\alpha/\alpha$ $\geq$ 4.5 $\times$ 10-8) can be achieved along cosmological distances with differential measurements of  $\Delta\alpha/\alpha$.

Key words: cosmology: observations -- line: profiles -- galaxies: quasars: absorption lines -- galaxies: quasars: individual: Q 1101-264 , HE 0515-4414

SIMBAD Objects

© ESO 2005

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.