Fundamental constants and high-resolution spectroscopy

Absorption-line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, , and the proton-to-electron mass ratio, = m(p)/m(e), as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in on cosmological scales which may reach a fractional level of approximate to 10 ppm (parts per million). We are conducting a Large Programme of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high-resolution (R approximate to 60000) and high signal-to-noise ratio (S/N approximate to 100) spectra calibrated specifically to study the variations of the fundamental constants. We here provide a general overview of the Large Programme and report on the first results for these two constants, discussed in detail in Molaro et al. (2013) and Rahmani et al. (2013). A stringent bound for / is obtained for the absorber at z(abs) = 1.6919 towards HE 2217-2818. The absorption profile is complex with several very narrow features, and is modeled with 32 velocity components. The relative variation in in this system is +1.3 +/- 2.4(stat) +/- 1.0(sys) ppm if Al II 1670 angstrom and three FeII transitions are used, and +1.1 +/- 2.6(stat) ppm in a slightly different analysis with only FeII transitions used. This is one of the tightest bounds on -variation from an individual absorber and reveals no evidence for variation in at the 3-ppm precision level (1 sigma confidence). The expectation at this sky position of the recently-reported dipolar variation of is (3.2-5.4) +/- 1.7 ppm depending on dipole model used and this constraint of / at face value is not supporting this expectation but not inconsistent with it at the 3 sigma level. For the proton-to-electron mass ratio the analysis of the H-2 absorption lines of the z(abs) approximate to 2.4018 damped Ly system towards HE 0027-1836 provides / = (-7.6 +/- 8.1(stat) +/- 6.3(sys)) ppm which is also consistent with a null variation. The cross-correlation analysis between individual exposures taken over three years and comparison with almost simultaneous asteroid observations revealed the presence of a possible wavelength dependent velocity drift as well as of inter-order distortions which probably dominate the systematic error and are a significant obstacle to achieve more accurate measurements. ((c) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)