A sub-ppm upper limit on the cosmological variations of the fine structure constant α

Vol. 706
3. Cosmology (including clusters of galaxies)

A sub-ppm upper limit on the cosmological variations of the fine structure constant α

Using molecular lines toward two lensed quasars at different, moderate redshifts, the paper presents the most stringent limits to date on the simultaneous variation of the fine structure constant and the proton-to-electron mass ratios for a lookback of about half of the Hubble time comparing two CH transitions and one water one for relative velocity shifts. The two sources are unique in regard to their strength and the observability of the subcomponents; one target was observed at several epochs to constrain possible time variations. A notable feature of the study is the detailed analysis of the contributing uncertainties.