Time variation of fine-structure constant constrained by [O iii] emission-lines at 1.1 < z < 3.7

Abstract

ABSTRACT [O iii] λλ4960,5008 doublet are often the strongest narrow emission lines in starburst galaxies and quasi-stellar objects (QSOs), and thus are a promising probe to possible variation of the fine-structure constant α over cosmic time. Previous such studies using QSOs optical spectra were limited to z < 1. In this work, we constructed a sample of 40 spectra of Ly α emitting galaxies (LAEs) and a sample of 46 spectra of QSOs at 1.09 < z < 3.73 using the VLT/X-Shooter near-infrared spectra publicly available. We measured the wavelength ratios of the two components of the spin-orbit doublet and accordingly calculated α(z) using two methods. Analysis on all of the 86 spectra yielded Δα/α = (− 3 ± 6) × 10−5 with respect to the laboratory α measurements, consistent with no variation over the explored time interval. If assuming a uniform variation rate, we obtained α−1dα/dt = (− 3 ± 6) × 10−15 yr−1 within the last 12 Gyr. Extensive tests indicate that α variation could be better constrained using starburst galaxies’ spectra than using QSO spectra in future studies.