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Register a new userConstraint on a variation of the proton-to-electron mass ratio from H2 absorption towards quasar Q2348-011
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Molecular hydrogen (H2) absorption features observed in the line-of-sight to Q2348-011 at redshift zabs = 2.426 are analysed for the purpose of detecting a possible variation of the proton-to-electron mass ratio mu=mp/me. By its structure Q2348-011 is the most complex analysed H2 absorption system at high redshift so far, featuring at least seven distinctly visible molecular velocity components. The multiple velocity components associated with each transition of H2 were modeled simultaneously by means of a comprehensive fitting method. The fiducial model resulted in dmu/mu = (-0.68 +/- 2.78) x 10^-5, showing no sign that mu in this particular absorber is different from its current laboratory value. Although not as tight a constraint as other absorbers have recently provided, this result is consistent with the results from all previously analysed H2-bearing sight-lines. Combining all such measurements yields a constraint of dmu/mu < 10^-5 for the redshift range z = (2--3).
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Molecular hydrogen transitions in the sub-damped Lyman alpha absorber at redshift z = 2.69, toward the background quasar SDSS J123714.60+064759.5, were analyzed in order to search for a possible variation of the proton-to-electron mass ratio mu over a cosmological time-scale. The system is composed of three absorbing clouds where 137 H2 and HD absorption features were detected. The observations were taken with the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph with a signal-to-noise ratio of 32 per 2.5 km/s pixel, covering the wavelengths from 356.6 to 409.5 nm. A comprehensive fitting method was used to fit all the absorption features at once. Systematic effects of distortions to the wavelength calibrations were analyzed in detail from measurements of asteroid and `solar twin spectra, and were corrected for. The final constraint on the relative variation in mu between the absorber and the current laboratory value is dmu/mu = (-5.4 pm 6.3 stat pm 4.0 syst) x 10^(-6), consistent with no variation over a look-back time of 11.4 Gyrs.
Molecular transitions recently discovered at redshift z_abs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, mu=m_p/m_e. Observed with the Keck telescope, the optical echelle spectrum has the highest resolving power and largest number (86) of H_2 transitions in such analyses so far. Also, (seven) HD transitions are used for the first time to constrain mu-variation. These factors, and an analysis employing the fewest possible free parameters, strongly constrain mus relative deviation from the current laboratory value: dmu/mu =(+5.6+/-5.5_stat+/-2.9_sys)x10^{-6}, indicating an insignificantly larger mu in the absorber. This is the first Keck result to complement recent null constraints from three systems at z_abs>2.5 observed with the Very Large Telescope. The main possible systematic errors stem from wavelength calibration uncertainties. In particular, distortions in the wavelength solution on echelle order scales are estimated to contribute approximately half the total systematic error component, but our estimate is model dependent and may therefore under or overestimate the real effect, if present. To assist future mu-variation analyses of this kind, and other astrophysical studies of H_2 in general, we provide a compilation of the most precise laboratory wavelengths and calculated parameters important for absorption-line work with H_2 transitions redwards of the hydrogen Lyman limit.
Far infrared fine-structure transitions of CI and CII and rotational transitions of CO are used to probe hypothetical variations of the electron-to-proton mass ratio mu = m_e/m_p at the epoch of reionization (z > 6). A constraint on Delta mu/mu = (mu_obs - mu_lab)/mu_lab = (0.7 +/- 1.2)x10^-5 (1sigma) obtained at <z> = 6.31 is the most stringent up-to-date limit on the variation of mu at such high redshift. For all available estimates of Delta mu/mu ranging between z = 0 and z = 1100, - the epoch of recombination, - a regression curve Delta mu/mu = k_mu (1+z)^p, with k_mu = (1.6 +/- 0.3) x10^-8 and p = 2.00 +/- 0.03, is deduced. If confirmed, this would imply a dynamical nature of dark matter/dark energy.
New PKS1830-211 radio frequency observations of methanol at a redshift of 0.88582 have established the most stringent limits on changes in the proton to electron mass ratio mu to date. The observations place the limit of (delta mu)/mu </= (0.0 +/- 1.0) x 10^{-7} which is approximately a factor of four lower than the previous lowest limit at a redshift of 0.6742. This stringent limit at a look back time of roughly half the age of the universe has profound implications for rolling scalar field cosmologies and the new physics that they require. Many of these cosmologies invoke a scalar field phi that is also coupled to the electromagnetic field causing the values of the fundamental constants, mu and the fine structure constant alpha to roll with time. If the lowest expected value of the coupling to mu, zeta_{mu}$ is invoked the new limit requires a limit on the dark energy equation of state parameter w such that w+1 </= 0.001 at a redshift of 0.88582. This eliminates almost all of the expected parameter space for such cosmologies and new physics that have a coupling to the electromagnetic field. In these cases the limit requires that w must be extremely close to -1 for the last half of the age of the universe or that the coupling of the rolling scalar field to mu and the electromagnetic field be significantly below or at the limit of its expected range. The new observations solidify the role of fundamental constants in providing probes of the possible cosmologies and new physics to explain the acceleration of the expansion of the universe.
Molecular transitions recently discovered at redshift z_abs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, mu=m_p/m_e. Observed with the Keck telescope, the optical spectrum has the highest resolving power and largest number (86) of H_2 transitions in such analyses so far. Also, (7) HD transitions are used for the first time to constrain mu-variation. These factors, and an analysis employing the fewest possible free parameters, strongly constrain mus relative deviation from the current laboratory value: dmu/mu =(+5.6+/-5.5_stat+/-2.7_sys)x10^{-6}. This is the first Keck result to complement recent constraints from three systems at z_abs>2.5 observed with the Very Large Telescope.
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