Constraints on the variation of the fine-structure constant at 3<z<10 with JWST emission-line galaxies

We present constraints on the spacetime variation of the fine-structure constant α at redshifts $3<z<10$ using JWST emission-line galaxies. The galaxy sample consists of 572 high-quality spectra with strong and narrow [O III] λλ4959,5007 doublet emission lines from 522 galaxies, including 267 spectra at $z>5$. The [O III] doublet lines are arguably the best emission lines to probe the variation in α. We divide our sample into 5 subsamples based on redshift and calculate the relative variation Δα/α for the individual subsamples. The calculated Δα/α values are consistent with zero within 1σ at all redshifts, suggesting no time variation in α above a level of (1-2) ×10⁻⁴ (1σ) in the past 13.2 billion years. When the whole sample is combined, the constraint is improved to be Δα/α = (0.4±0.7) ×10⁻⁴. We further test the spatial variation in α using four subsamples of galaxies in four different directions on the sky. The measured Δα/α values are consistent with zero at a 1σ level of ~10⁻⁴. While the constraints in this work are not as stringent as those from lower-redshift quasar absorption lines in previous studies, this work uses an independent tracer and provides the first constraints on Δα/α at the highest redshifts. Our analyses also indicate that the relative wavelength calibration of the JWST spectra is robust. With the growing number of emission-line galaxies from JWST, we expect to achieve stronger constraints in the future.