New constraint on cosmological variation of the proton-to-electron mass ratio from Q0528-250

TL;DR

This study uses high-redshift quasar spectra to place new constraints on the possible variation of the proton-to-electron mass ratio over cosmological time, incorporating HD detection for the first time.

Contribution

It presents the first detection of HD in a high-redshift absorber and constrains the variation of the proton-to-electron mass ratio using combined H2 and HD transitions.

Findings

No significant variation in μ detected within uncertainties.

HD detection enhances sensitivity to μ variation.

Systematic uncertainties dominated by wavelength calibration.

Abstract

Molecular hydrogen transitions in quasar spectra can be used to constrain variation in the proton-to-electron mass ratio, $\mu\equiv m_p/m_e$, at high redshifts ($z\gtrsim 2$). We present here an analysis of a new spectrum of the quasar Q0528$-$250, obtained on VLT/UVES (the Ultraviolet and Visual Echelle Spectrograph, on the Very Large Telescope), and analyse the well-known H$_2$ absorber at $z=2.811$ in this spectrum. For the first time we detect HD (deuterated molecular hydrogen) in this system with a column density of $\log_{10}(N/\mathrm{cm^{-2}})=13.27 \pm 0.07$; HD is sensitive to variation in $\mu$, and so we include it in our analysis. Using 76 H$_2$ and 7 HD transitions we constrain variation in $\mu$ from the current laboratory value to be $\Delta\mu/\mu = (0.3\pm 3.2_\mathrm{stat} \pm 1.9_\mathrm{sys})\times 10^{-6}$, which is consistent with no cosmological variation in $\mu$, as well as with previous results from other H$_2$/HD absorbers. The main sources of systematic uncertainty relate to accurate wavelength calibration of the spectra and the re-dispersion of multiple telescope exposures onto the one pixel grid.