Conjugate 18 cm OH satellite lines at a cosmological distance

Stringent Constraints on Fundamental Constant Evolution Using Conjugate 18 cm Satellite OH Lines

We have used the Arecibo Telescope to carry out one of the deepest-ever integrations in radio astronomy, targeting the redshifted conjugate satellite OH 18 cm lines at z≈0.247 towards PKS 1413+135. The satellite OH 1720 and 1612 MHz lines are, respectively, in emission and absorption, with exactly the same line shapes due to population inversion in the OH ground state levels. Since the 1720 and 1612 MHz line rest frequencies have different dependences on the fine structure constant α and the proton-electron mass ratio μ, a comparison between their measured redshifts allows one to probe changes in α and μ with cosmological time. In the case of conjugate satellite OH 18 cm lines, the predicted perfect cancellation of the sum of the line optical depths provides a strong test for the presence of systematic effects that might limit their use in probing fundamental constant evolution. A nonparametric analysis of our new Arecibo data yields [ΔX/X]=(+0.97±1.52)×10^{-6}, where X≡μα^{2}. Combining this with our earlier results from the Arecibo Telescope and the Westerbork Synthesis Radio Telescope, we obtain [ΔX/X]=(-1.0±1.3)×10^{-6}, consistent with no changes in the quantity μα^{2} over the last 2.9 Gyr. This is the most stringent present constraint on fractional changes in μα^{2} from astronomical spectroscopy, and with no evidence for systematic effects.

Limit on the cosmological variation of mp/me from the inversion spectrum of ammonia

We obtain the limit on the space-time variation of the ratio of the proton mass to the electron mass, mu=m(p)/m(e), based on comparison of quasar absorption spectra of NH3 with CO, HCO+ and HCN rotational spectra. For the inversion transition in NH3 (lambda approximately 1.25 cm(-1)) the relative frequency shift is significantly enhanced: deltaomega/omega=-4.46deltamu/mu. This enhancement allows one to increase sensitivity to the variation of mu using NH3 spectra for high redshift objects. We use published data on microwave spectra of the object B0218+357 to place the limit deltamu/mu=(0.6+/-1.9) x 10(-6) at redshift z=0.6847; this limit is several times better than the limits obtained by different methods and may be significantly improved. Assuming linear time dependence we obtain mu/mu=(-1+/-3) x 10(-16) yr(-1).

Cold molecule spectroscopy for constraining the evolution of the fine structure constant

We report precise measurements of ground-state, Lambda-doublet microwave transitions in the hydroxyl radical molecule (OH). Utilizing slow, cold molecules produced by a Stark decelerator we have improved over the precision of the previous best measurement 25-fold for the F'=2-->F=2 transition, yielding (1 667 358 996 +/- 4)Hz, and by tenfold for the F'=1-->F=1 transition, yielding (1 665 401 803 +/-12)Hz. Comparing these laboratory frequencies to those from OH megamasers in interstellar space will allow a sensitivity of 1 ppm for Delta(alpha/alpha) over approximately 10(10) yr.

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

We have detected the four 18 cm OH lines from the z approximaetely 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 approximately 0.765 absorber and the z approximately 0.685 lens toward B0218 + 357 to place stringent constraints on changes in F triple-bond g(p)[alpha(2)/mu](1.57). We obtain [DeltaF/F] = (0.44 +/- 0.36(stat) +/- 1.0(sys)t) x 10(-5), consistent with no evolution over the redshift range 0 < z < or = 0.7. The measurements have a 2sigma sensitivity of [Deltaalpha/alpha] < 6.7 x 10(-6) or [Deltamu/mu] < 1.4 x 10(-5) to fractional changes in alpha and mu over a period of approximately 6.5 G yr, half the age of the Universe. These are among the most sensitive constraints on changes in mu.