SIMBAD references

Molecular hydrogen transitions in quasar spectra can be used to constrain variation in the proton-to-electron mass ratio, µ ≡= m_p/m_e, at high redshifts (z ≳ 2). We present here an analysis of a new spectrum of the quasar Q0528-250, obtained on Very Large Telescope (VLT)/Ultraviolet and Visual Echelle Spectrograph (UVES), and analyse the well-known H₂ absorber at z = 2.811 in this spectrum. For the first time we detect deuterated molecular hydrogen (HD) in this system with a column density of log₁₀(N/cm2) = 13.27±0.07; HD is sensitive to variation in µ, and so we include it in our analysis. Using 76 H₂ and seven HD transitions we constrain variation in µ from the current laboratory value to be Δµ/µ= (0.3±3.2_stat± 1.9_sys) {x} 10^–6, which is consistent with no cosmological variation in µ, as well as with previous results from other H₂/HD absorbers. The main sources of systematic uncertainty relate to accurate wavelength calibration of the spectra and the re-dispersion of multiple telescope exposures on to the one pixel grid.