QSO 0347-383 and the invariance of m_p/m_e in the course of cosmic time

TL;DR

This study investigates whether the proton-to-electron mass ratio has varied over cosmic time by analyzing molecular hydrogen lines in quasar spectra, finding no significant variation within measurement uncertainties.

Contribution

It provides the first correction for inter-order distortions in such measurements and highlights the importance of systematic error assessment in constraining fundamental constant variations.

Findings

No significant variation of mu observed at z=3.025

Systematic errors can impact line position measurements up to 220 m/s

Corrections for spectral distortions are crucial for accurate results

Abstract

The variation of the dimensionless fundamental physical constant mu = m_p/m_e (the proton to electron mass ratio) can be constrained via observation of Lyman and Werner lines of molecular hydrogen in the spectra of damped Lyman alpha systems (DLAs) in the line of sight to distant QSOs. Drawing on VLT-UVES high resolution data sets of QSO 0347-383 and its DLA obtained in 2009 our analysis yields dmu/mu = (4.3 +/- 7.2) * 10^-6 at z_abs =3.025. We apply corrections for the observed offsets between discrete spectra and for the first time we find indications for inter-order distortions. Current analyses tend to underestimate the impact of systematic errors. Based on the scatter of the measured redshifts and the corresponding low significance of the redshift-sensitivity correlation we estimate the limit of accuracy of line position measurements to about 220 m/s, consisting of roughly 150 m/s due to the uncertainty of the absorption line fit and about 150 m/s allocated to systematics related to instrumentation and calibration.