Measuring the Time Variation of the Fine-structure Constant with Quasars Detected by LAMOST

Abstract The [O iii ] λλ 4960, 5008 emission lines in the optical spectra of galaxies and quasars have been widely used to investigate the possible variation of the fine-structure constant α over cosmic time. In this work, we utilize the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) quasar survey, for the first time, to measure the relative α variation Δ α / α in time through the [O iii ] doublet method. From the LAMOST Data Release 9 quasar catalog, we refine a sample of 209 quasar spectra with strong and narrow [O iii ] emission lines over a redshift range of 0 < z < 0.8. Analysis on all of the 209 spectra obtains Δ α / α = (0.5 ± 3.7) × 10 −4 , which suggests that there is no evidence of varying α on the explored cosmological timescales. Assuming a linear variation, the mean rate of change in Δ α / α is limited to be (−3.4 ± 2.4) × 10 −13 yr −1 in the last 7.0 Gyr. While our LAMOST-based constraint on Δ α / α is not competitive with those of the Sloan Digital Sky Survey (SDSS) quasar observations, our analysis serves to corroborate the results of SDSS with another independent survey.