2008/07/31 by Enrique Gaztanaga, Anna Cabre, Lam Hui · 3 citations
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2009.15405.x
Minor revision to match version accepted for publication in MNRAS. Includes comparison to DR7, a Table with the measurements and errors. Includes extended analysis on systematic errors. Some figures have been omitted. Main results and conclusions remain unchanged
arxiv created 2009/07/16 · arxiv updated 2015/05/12
We study the clustering of LRG galaxies in the latest spectroscopic SDSS data releases, DR6 and DR7, which sample over 1 Gpc3/h3 to z=0.47. The 2-point correlation function \xisp is estimated as a function of perpendicular σ and line-of-sight π (radial) directions. We find a significant detection of a peak at r≃ 110Mpc/h, which shows as a circular ring in the σ-π plane. There is also significant evidence for a peak along the radial direction whose shape is consistent with its originating from the recombination-epoch baryon acoustic oscillations (BAO). A \xisp model with no radial BAO peak is disfavored at 3.2σ, whereas a model with no magnification bias is disfavored at 2σ. The radial data enable, for the first time, a direct measurement of the Hubble parameter H(z) as a function of redshift. This is independent from earlier BAO measurements which used the spherically averaged (monopole) correlation to constrain an integral of H(z). Using the BAO peak position as a standard ruler in the radial direction, we find: H(z=0.24)= 79.69 ± 2.32 (± 1.29) km/s/Mpc for z=0.15-0.30 and H(z=0.43)= 86.45 ± 3.27 (± 1.69) km/s/Mpc for z=0.40-0.47. The first error is a model independent statistical estimation and the second accounts for systematics both in the measurements and in the model. For the full sample, z=0.15-0.47, we find H(z=0.34)= 83.80 ± 2.96 (± 1.59) km/s/Mpc.