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Register a new userNew limit on a varying proton-to-electron mass ratio from high-resolution optical quasar spectra
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Adrian L. Malec
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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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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 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).
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.
A molecular hydrogen absorber at a lookback time of 12.4 billion years, corresponding to 10$%$ of the age of the universe today, is analyzed to put a constraint on a varying proton--electron mass ratio, $mu$. A high resolution spectrum of the J1443$+$2724 quasar, which was observed with the Very Large Telescope, is used to create an accurate model of 89 Lyman and Werner band transitions whose relative frequencies are sensitive to $mu$, yielding a limit on the relative deviation from the current laboratory value of $Deltamu/mu=(-9.5pm5.4_{textrm{stat}} pm 5.3_{textrm{sys}})times 10^{-6}$.
Rovibronic molecular hydrogen (H$_2$) transitions at redshift $z_{rm abs} simeq 2.659$ towards the background quasar B0642$-$5038 are examined for a possible cosmological variation in the proton-to-electron mass ratio, $mu$. We utilise an archival spectrum from the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph with a signal-to-noise ratio of $sim$35 per 2.5-km$,$s$^{-1}$ pixel at the observed H$_2$ wavelengths (335--410 nm). Some 111 H$_2$ transitions in the Lyman and Werner bands have been identified in the damped Lyman $alpha$ system for which a kinetic gas temperature of $sim$84 K and a molecular fraction $log f = -2.18pm0.08$ is determined. The H$_2$ absorption lines are included in a comprehensive fitting method, which allows us to extract a constraint on a variation of the proton-electron mass ratio, $Deltamu/mu$, from all transitions at once. We obtain $Deltamu/mu = (17.1 pm 4.5_{rm stat} pm3.7_{rm sys})times10^{-6}$. However, we find evidence that this measurement has been affected by wavelength miscalibration errors recently identified in UVES. A correction based on observations of objects with solar-like spectra gives a smaller $Deltamu/mu$ value and contributes to a larger systematic uncertainty: $Deltamu/mu = (12.7 pm 4.5_{rm stat} pm4.2_{rm sys})times10^{-6}$.
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