An upper limit on possible time variation of the fine-structure constant from qso absorption spectra

Abstract

Abstract A statistical analysis of 1185 fine splittings of CIV, NV, OVI, MgII, AlIII and SiIV doublet absorption lines with redshifts z = 0.2–3.7 in QSO spectra is carried out in order to estimate a possible time variation of the fine-structure constant α = e2/hc at cosmological time scales t ∼101° yr. Robust statistical estimates like the “trimmed mean” are used as well as least squares. No statistically significantly time variations of α is found. The estimate α−1 dα/dz = (-1.2 ± 2.9) × 10−4 is obtained. For the 95% confidence level, the upper limit on the rate of a relative variation of the fine-structure constant is |α−1 dα/dz| < 6.4 × 10−4, which approximately corresponds to |α−1dα/dt| < 4 × 10−14 yr−1. This limit reprents the strongest up-to-date restriction on the possible time variation of α for the epoch 0.2 ≤ z ≤ 4.