An order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant a. Applied to a sample of 30 absorption systems, spanning redshifts 0.5 , z , 1.6, we derive limits on variations in a over a wide range of epochs. For the whole sample, Da͞a ͑21.1 6 0.4͒ 3 10 25 . This deviation is dominated by measurements at z . 1, where Da͞a ͑21.9 6 0.5͒ 3 10 25 . For z , 1, Da͞a ͑20.2 6 0.4͒ 3 10 25 . While this is consistent with a time-varying a, further work is required to explore possible systematic errors in the data, although careful searches have so far revealed none. [S0031-9007(98)08267-2] PACS numbers: 06.20. Jr, 95.30.Dr, 95.30.Sf, 98.80.Es There are several theoretical motivations to search for space-time variations in the fine structure "constant," a. Theories which attempt to unify gravity and other fundamental forces may require the existence of additional compact space dimensions. Any cosmological evolution in the mean scale factor of these additional dimensions will manifest itself as a time variation of our bare three-dimensional coupling constants [1]. Alternatively, theories have been considered which introduce new scalar fields whose couplings with the Maxwell scalar F ab F ab allow a time-varying a [2]. The measurement of any variation in a would clearly have profound implications for our understanding of fundamental physics.Spectroscopic observations of gas clouds seen in absorption against background quasars can be used to search for time variation of a. Analyses involving optical spectroscopy of quasar absorbers have concentrated on the relativistic fine-structure splitting of alkali-type doublets; the separation between lines in one multiplet is proportional to a 2 , so small variations in the separation are directly proportional to a, to a good approximation.While the simplicity of that method is appealing, the relativistic effect causing the fine splitting is small, restricting the potential accuracy. We demonstrate below how a substantial sensitivity gain is achieved by comparing the wavelengths of lines from different species, and develop a new procedure, simultaneously analyzing the Mg II 2796͞2803 doublet and up to five Fe II transitions (Fe II 2344, 2374, 2383, 2587, 2600 Å) from three different multiplets. These particular transitions are chosen for the following reasons: (i) They are commonly seen in quasar absorption systems; (ii) they fall into and span a suitable rest-wavelength range; (iii) an excellent database was available [3]; (iv) extremely precise laboratory wavelengths have been measured; and (v) the large Fe and Mg nuclear charge difference yields a considerable sensitivity gain.We describe the details of the theoretical developments in a separate paper [4], here summarizing the main points. The energy equation for a transition from the ground state within a particular multiplet, observed at some redshift z, is given bywhere Z is the nuclear charge, L and S are the electron total orbital ...

We present measurements of the baryon acoustic peak at redshifts z = 0.44, 0.6 and 0.73 in the galaxy correlation function of the final data set of the WiggleZ Dark Energy Survey. We combine our correlation function with lower redshift measurements from the 6-degree Field Galaxy Survey and Sloan Digital Sky Survey, producing a stacked survey correlation function in which the statistical significance of the detection of the baryon acoustic peak is 4.9σ relative to a zero-baryon model with no peak. We fit cosmological models to this combined baryon acoustic oscillation (BAO) data set comprising six distance-redshift data points, and compare the results with similar cosmological fits to the latest compilation of supernovae (SNe) and cosmic microwave background (CMB) data. The BAO and SNe data sets produce consistent measurements of the equation-of-state w of dark energy, when separately combined with the CMB, providing a powerful check for systematic errors in either of these distance probes. Combining all data sets we determine w = −1.03 ± 0.08 for a flat universe, consistent with a cosmological constant model. Assuming dark energy is a cosmological constant and varying the spatial curvature, we find k = −0.004 ± 0.006.

The definitive version can be found at: http://onlinelibrary.wiley.com/ Copyright Royal Astronomical SocietyThe Galaxy and Mass Assembly (GAMA) survey has been operating since 2008 February on the 3.9-m Anglo-Australian Telescope using the AAOmega fibre-fed spectrograph facility to acquire spectra with a resolution of R approximate to 1300 for 120 862 Sloan Digital Sky Survey selected galaxies. The target catalogue constitutes three contiguous equatorial regions centred at 9h (G09), 12h (G12) and 14.5h (G15) each of 12 x 4 deg2 to limiting fluxes of r(pet) < 19.4, r(pet) < 19.8 and r(pet) < 19.4 mag, respectively (and additional limits at other wavelengths). Spectra and reliable redshifts have been acquired for over 98 per cent of the galaxies within these limits. Here we present the survey footprint, progression, data reduction, redshifting, re-redshifting, an assessment of data quality after 3 yr, additional image analysis products (including ugrizYJHK photometry, Sersic profiles and photometric redshifts), observing mask and construction of our core survey catalogue (GamaCore). From this we create three science-ready catalogues: GamaCoreDR1 for public release, which includes data acquired during year 1 of operations within specified magnitude limits (2008 February to April); GamaCoreMainSurvey containing all data above our survey limits for use by the GAMA Team and collaborators; and GamaCoreAtlasSV containing year 1, 2 and 3 data matched to Herschel-ATLAS science demonstration data. These catalogues along with the associated spectra, stamps and profiles can be accessed via the GAMA website: http://www.gama-survey.org/

We perform a joint determination of the distance–redshift relation and cosmic expansion rate at redshifts z = 0.44, 0.6 and 0.73 by combining measurements of the baryon acoustic peak and Alcock–Paczynski distortion from galaxy clustering in the WiggleZ Dark Energy Survey, using a large ensemble of mock catalogues to calculate the covariance between the measurements. We find that DA(z) = (1205 ± 114, 1380 ± 95, 1534 ± 107) Mpc and H(z) = (82.6 ± 7.8, 87.9 ± 6.1, 97.3 ± 7.0) km s−1 Mpc−1 at these three redshifts. Further combining our results with other baryon acoustic oscillation and distant supernovae data sets, we use a Monte Carlo Markov Chain technique to determine the evolution of the Hubble parameter H(z) as a stepwise function in nine redshift bins of width Δz = 0.1, also marginalizing over the spatial curvature. Our measurements of H(z), which have precision better than 7 per cent in most redshift bins, are consistent with the expansion history predicted by a cosmological constant dark energy model, in which the expansion rate accelerates at redshift z < 0.7.

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