First Constraint on Cosmological Variation of the Proton-to-Electron Mass Ratio from Two Independent Telescopes

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 Ultraviolet and Visual Echelle Spectrograph on the European Southern Observatory Very Large Telescope (Paranal, Chile). This delivers a constraint on a possible variation of the proton-to-electron mass ratio of ${Δ}{μ}/{μ}=(8.5±{}{3.6}ₛₜₐₜ±{}{2.2}syst)×{}{10}^{{-}6}$ at redshift ${z}abs=2.059$, which agrees well with a recently published result on the same system observed at the Keck telescope yielding ${Δ}{μ}/{μ}=(5.6±{}{5.5}ₛₜₐₜ±{}{2.9}syst)×{}{10}^{{-}6}$. Both analyses used the same robust absorption line fitting procedures with detailed consideration of systematic errors.