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 /= (8. 53. 6ₒₓ₀ₓ2. 2ₒₘₒₓ) 10^-6 at redshift z₀₁ₒ=2. 059, which agrees well with a recently published result on the same system observed at the Keck telescope yielding /= (5. 65. 5ₒₓ₀ₓ2. 9ₒₘₒₓ) 10^-6. Both analyses used the same robust absorption line fitting procedures with detailed consideration of systematic errors.