Issue |
A&A
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 |
VLT/UVES constraints on the cosmological variability of the fine-structure constant
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 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
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