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 Δμ/μ=(8.5±3.6stat±2.2syst)×10-6 at redshift zabs=2.059, which agrees well with a recently published result on the same system observed at the Keck telescope yielding Δμ/μ=(5.6±5.5stat±2.9syst)×10-6. Both analyses used the same robust absorption line fitting procedures with detailed consideration of systematic errors.