Abstract

Precise radial velocity measurements (?v/c ? 10-7) of Fe II lines in damped Ly? systems from very high quality VLT/ UVES spectra of quasars HE 0515-4414 and Q 1101-264 are used to probe cosmological time dependence of the fine structure constant, ?. It is found that between two redshifts z1 = 1.15, and z2 = 1.84, the value of ??/? changes at the level of a few ppm: (?z2 - ?z1)/?0 = 5.43 ± 2.52, ppm. Variations of ? can be considered as one of the most reliable method to constrain the dark energy equation of state and improvements on the accuracy of the wavelength calibration of QSO spectra are of great importance. © 2008 Springer-Verlag Berlin Heidelberg.