• methods: data analysis;
  • quasars: absorption lines;
  • cosmology: observations


Molecular hydrogen (H2) absorption features observed in the line of sight to Q2348−011 at redshift zabs≃ 2.426 are analysed for the purpose of detecting a possible variation of the proton-to-electron mass ratio μ≡mp/me. By its structure, Q2348−011 is the most complex analysed H2 absorption system at high redshift so far, featuring at least seven distinctly visible molecular velocity components. The multiple velocity components associated with each transition of H2 were modelled simultaneously by means of a comprehensive fitting method. The fiducial model resulted in Δμ/μ= (−0.68 ± 2.78) × 10−5, showing no sign that μ in this particular absorber is different from its current laboratory value. Although not as tight a constraint as other absorbers have recently provided, this result is consistent with the results from all previously analysed H2-bearing sightlines. Combining all such measurements yields a constraint of |Δμ/μ|≤ 10−5 for the redshift range z= 2–3.