Astrophysical Constraintson Hypothetical Variabilityof Fundamental Constants

Abstract

Applied to three inhomogeneous samples of quasar absorption-line spectra, the many-multiplet method gives a shift in the value of the fine-structure constant of Δα/α = (–5.4±1.2)×10^–6 in the redshift range 0.2 < z < 3.7 (Sydney group). The 1σ error claimed in these calculations is, however, much too small and cannot be maintained by current observations of quasars. We present a modified many-multiplet method to set an upper limit on Δα/α from a homogeneous sample of Fe ii lines identified in the up-to-date best quality spectrum of the quasar HE 0515–4414. Our result is Δα/α = (1.1±1.1)×10^–5 at z = 1.149. Theoretical models of the fundamental physical interactions predict that the proton-to-electron mass ratio (μ = m_p/m_e) may relate to the shift in Δα/α as $\Delta\mu/\mu = {\cal R}\,\Delta\alpha/\alpha$. We use high-resolution observations of molecular hydrogen H₂ ultraviolet absorption lines at z = 3.025 toward the quasar Q 0347–3818 to bound the value of ${\cal R}$. The obtained constraints on Δ ln μ = (2.1±3.6)×10^–5 and on Δln α = (1.1±1.1)×10^–5 rule out vary large values of $|{\cal R}| > 6$. Future observations with a new High Accuracy Radial velocity Planet Searcher spectrograph may provide a crucial test for the Δα/α measurements at a level of 10^–6.