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

Abstract

We have detected the four 18cm OH lines from the $z \sim 0.765$ 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 $z \sim 0.765$ absorber and the $z \sim 0.685$ lens toward B0218+357 to place stringent constraints on changes in $F \equiv g_p [α^2/μ]^{1.57}$. We obtain $[ΔF/F] = (0.44 \pm 0.36^{\rm stat} \pm 1.0^{\rm syst}) \times 10^{-5}$, consistent with no evolution over the redshift range $0 < z < 0.7$. The measurements have a $2 σ$ sensitivity of $[Δα/α] < 6.7 \times 10^{-6}$ or $[Δμ/μ] < 1.4 \times 10^{-5}$ to fractional changes in $α$ and $μ$ over a period of $\sim 6.5$ Gyr, half the age of the Universe. These are among the most sensitive current constraints on changes in $μ$.