Constraints on changes in fundamental constants from a cosmologically distant OH absorber or emitter

Abstract

We have detected the four 18 cm OH lines from the z ∼ 0.765 gravitational lens toward PMN J0134–0931. The 1612 and 1720 MHz lines are in conjugate absorption and emission, providing a laboratory to test the evolution of fundamental constants over a large lookback time. We compare the HI and OH main line absorption redshifts of the different components in the z ∼ 0.765 absorber and the z ∼ 0.685 lens toward B0218+357 to place stringent constraints on changes in F ≡ gp [α²/μ]1.57. We obtain [ΔF/F] = (0.44 ± 0.36^stat ± 1.0^syst)×10⁻⁵, consistent with no evolution over the redshift range 0 < z ≲ 0.7. The measurements have a 2σ sensitivity of [Δα/α] <6.7×10⁻⁶ or [Δμ/μ]<1.4×10⁻⁵ to fractional changes in α and μ over a period of ∼6.5  G yr, half the age of the Universe. These are among the most sensitive constraints on changes in μ.