VLT/UVES constraints on the cosmological variability of the fine-structure constant
Abstract
A differential many-multiplet (DMM) technique is developed to probe the variability of alpha. Applied to the FeII lines of the metal absorption line system at zabs = 1.839 in the spectrum of Q1101-264 obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT), the DMM provides da/a = (2.4+/-3.8) 10^{-6}.The zabs = 1.15 FeII system toward HE0515-4414 has been re-analyzed by the DMM method thus obtaining for the combined sample da/a = (0.4+/-1.5) 10^{-6}. These values are shifted with respect to the Keck/HIRES mean da/a = (-5.7+/-1.1) 10^{-6} (Murphy et al. 2004) at very high confidence level (95%). The fundamental photon noise limitation in the da/a 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 resolution coupled to a 100m class telescope the present Oklo level (da/a >= 4.5 10^{-8}) can be achieved along cosmological distances with differential measurements of da/a.Keywords
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