Date Published:

April 1, 2013

Abstract:

We report a detection of the baryon acoustic oscillation (BAO) featurein the three-dimensional correlation function of the transmitted fluxfraction in the Lyα forest of high-redshift quasars. The studyuses 48 640 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from theBaryon Oscillation Spectroscopic Survey (BOSS) of the third generationof the Sloan Digital Sky Survey (SDSS-III). At a mean redshift z = 2.3,we measure the monopole and quadrupole components of the correlationfunction for separations in the range 20 h^-1 Mpc < r <200 h^-1 Mpc. A peak in the correlation function is seen at aseparation equal to (1.01 ± 0.03) times the distance expected forthe BAO peak within a concordance ΛCDM cosmology. This firstdetection of the BAO peak at high redshift, when the universe wasstrongly matter dominated, results in constraints on the angulardiameter distance D_A and the expansion rate H at z = 2.3that, combined with priors on H₀ and the baryon density,require the existence of dark energy. Combined with constraints derivedfrom cosmic microwave background observations, this result implies H(z =2.3) = (224 ± 8) km s^-1 Mpc^-1, indicatingthat the time derivative of the cosmological scale parameter ȧ =H(z = 2.3)/(1 + z) is significantly greater than that measured with BAOat z ~ 0.5. This demonstrates that the expansion was decelerating in therange 0.7 < z < 2.3, as expected from the matter domination duringthis epoch. Combined with measurements of H₀, one sees thepattern of deceleration followed by acceleration characteristic of adark-energy dominated universe.Appendices are available in electronic form at http://www.aanda.org

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