AN OBSERVATIONAL DETERMINATION OF THE PROTON TO ELECTRON MASS RATIO IN THE EARLY UNIVERSE

作者：Thompson Rodger I^*; Bechtold Jill; Black John H; Eisenstein Daniel; Fan Xiaohui; Kennicutt Robert C; Martins Carlos; Prochaska J Xavier; Shirley Yancey L

来源：Astrophysical Journal, 2009, 703(2): 1648-1662.

DOI：10.1088/0004-637X/703/2/1648

• early universe

In an effort to resolve the discrepancy between two measurements of the fundamental constant mu, the proton to electron mass ratio, at early times in the universe we reanalyze the same data used in the earlier studies. Our analysis of the molecular hydrogen absorption lines in archival Very Large Telescope/Ultraviolet and Visible Echelle Spectrometer (UVES) spectra of the damped Lyman alpha systems in the quasi-stellar objects Q0347383 and Q0405-443 yields a combined measurement of a Delta mu/mu value of (-7 +/- 8) x 10(-6), consistent with no change in the value of mu over a time span of 11.5 Gyr. Here, we define Delta mu as (mu(z) - mu(0)) where mu(z) is the value of mu at a redshift of z and mu(0) is the present-day value. Our null result is consistent with the recent measurements of King et al., Delta mu/mu = (2.6 +/- 3.0) x 10(-6), and inconsistent with the positive detection of a change in mu by Reinhold et al. Both of the previous studies and this study are based on the same data but with differing analysis methods. Improvements in the wavelength calibration over the UVES pipeline calibration is a key element in both of the null results. This leads to the conclusion that the fundamental constant mu is unchanged to an accuracy of 10(-5) over the last 80% of the age of the universe, well into the matter dominated epoch. This limit provides constraints on models of dark energy that invoke rolling scalar fields and also limits the parameter space of supersymmetric or string theory models of physics. New instruments, both planned and under construction, will provide opportunities to greatly improve the accuracy of these measurements.

• 出版日期2009-10-1