Constraints on the spacetime variation of the fine-structure constant using DESI emission-line galaxies

Understand

We present strong constraints on the spacetime variation of the fine-structure constant $\alpha$ using the Dark Energy Spectroscopic Instrument (DESI).

• In this pilot work, we utilize $\sim110,000$ galaxies with strong and narrow O III $\lambda\lambda$4959,5007 emission lines to measure the relative variation $\Delta\alpha/\alpha$ in space and time.
• The O III doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies.
• Our galaxy sample spans a redshift range of $0<z<0.95$, covering half of all cosmic time.