Constraint on a variation of the proton-to-electron mass ratio from H2 absorption towards quasar Q2348-011

Molecular hydrogen (H₂) absorption features observed in the line of sight to Q2348-011 at redshift z_abs≃ 2.426 are analysed for the purpose of detecting a possible variation of the proton-to-electron mass ratio μ≡m_p/m_e. 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.