First constraint on cosmological variation of the proton-to-electron mass ratio from two independent telescopes

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A high signal-to-noise spectrum covering the largest number of hydrogen lines (90 H2 lines and 6 HD lines) in a high redshift object was analyzed from an observation along the sight-line to the bright quasar source J2123-005 with the UVES spectrograph on the ESO Very Large Telescope (Paranal, Chile). This delivers a constraint on a possible variation of the proton-to-electron mass ratio of Dmu/mu = (8.5 ± 3.6stat ± 2.2syst) x 10⁻⁶ at redshift z=2.059, which agrees well with a recently published result on the same system observed at the Keck telescope yielding Dmu/mu = (5.6 ± 5.5stat ± 2.9syst) x 10⁻⁶. Both analyses used the same robust absorption line fitting procedures with detailed consideration of systematic errors.