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

TL;DR

This study uses JWST emission-line galaxy spectra to constrain potential variations in the fine-structure constant across high redshifts, finding no significant change over the past 13 billion years.

Contribution

First constraints on the variation of the fine-structure constant at redshifts 2.5 to 9.5 using JWST emission-line galaxies, expanding the redshift range of previous measurements.

Findings

No significant variation in $\alpha$ detected at all redshifts.

Combined data constrains $\\Delta\\alpha/\\alpha$ to (0.2 ± 0.7) × 10^{-4}.

Spatial variation tests are consistent with zero within $2 imes 10^{-4}$.

Abstract

We present constraints on the spacetime variation of the fine-structure constant $\alpha$ at redshifts $2.5\le z<9.5$ using JWST emission-line galaxies. The galaxy sample consists of 621 high-quality spectra with strong and narrow [O III] $\lambda\lambda$4959,5007 doublet emission lines from 578 galaxies, including 232 spectra at $z>5$. The [O III] doublet lines are arguably the best emission lines to probe the variation in $\alpha$. We divide our sample into six subsamples based on redshift and calculate the relative variation $\Delta\alpha/\alpha$ for the individual subsamples. The calculated $\Delta\alpha/\alpha$ values are consistent with zero within $1\sigma$ at all redshifts, suggesting no time variation in $\alpha$ above a level of $(1-2) \times10^{-4}$ ($1\sigma$) in the past 13.2 billion years. When the whole sample is combined, the constraint is improved to be $\Delta\alpha/\alpha = (0.2\pm0.7) \times10^{-4}$. We further test the spatial variation in $\alpha$ using four subsamples of galaxies in four different directions on the sky. The measured $\Delta\alpha/\alpha$ values are consistent with zero at a $1\sigma$ level of $\sim 2\times10^{-4}$. 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 $\Delta\alpha/\alpha$ at the highest redshifts. With the growing number of emission-line galaxies from JWST, we expect to achieve stronger constraints in the future.