Baryon acoustic oscillations in the Sloan Digital Sky Survey Data Release 7 galaxy sample

Abstract

The spectroscopic Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) galaxy sample represents the final set of galaxies observed using the original SDSS target selection criteria. We analyse the clustering of galaxies within this sample, including both the luminous red galaxy and main samples, and also include the 2‐degree Field Galaxy Redshift Survey data. In total, this sample comprises 893 319 galaxies over 9100 deg2. Baryon acoustic oscillations (BAO) are observed in power spectra measured for different slices in redshift; this allows us to constrain the distance–redshift relation at multiple epochs. We achieve a distance measure at redshift z= 0.275, of rs(zd)/DV(0.275) = 0.1390 ± 0.0037 (2.7 per cent accuracy), where rs(zd) is the comoving sound horizon at the baryon‐drag epoch, DV(z) ≡[(1 +z)2D2Acz/H(z)]1/3, DA(z) is the angular diameter distance and H(z) is the Hubble parameter. We find an almost independent constraint on the ratio of distances DV(0.35)/DV(0.2) = 1.736 ± 0.065, which is consistent at the 1.1σ level with the best‐fitting Λ cold dark matter model obtained when combining our z= 0.275 distance constraint with the Wilkinson Microwave Anisotropy Probe 5‐year (WMAP5) data. The offset is similar to that found in previous analyses of the SDSS DR5 sample, but the discrepancy is now of lower significance, a change caused by a revised error analysis and a change in the methodology adopted, as well as the addition of more data. Using WMAP5 constraints on Ωbh2 and Ωc h2, and combining our BAO distance measurements with those from the Union supernova sample, places a tight constraint on Ωm= 0.286 ± 0.018 and H0= 68.2 ± 2.2 km s−1 Mpc−1 that is robust to allowing Ωk≠ 0 and w≠−1. This result is independent of the behaviour of dark energy at redshifts greater than those probed by the BAO and supernova measurements. Combining these data sets with the full WMAP5 likelihood constraints provides tight constraints on both Ωk=−0.006 ± 0.008 and w=−0.97 ± 0.10 for a constant dark energy equation of state.

Constraining the cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data

“…The difference in the BAO dataset used in this work from that used in [4] (see Table 1 in this reference) is that here we dropped the measurements from [43] at z = 0.2 (which has one of the largest errors) and at z = 0.35. We considered instead the more precise estimates at z = 0.35 from [13] and at z = 0.57 from [14].…”

Observational probes of cosmic acceleration

“…Prominent examples include the supernova and weak lensing programs of the CFHT Legacy Survey (CFHTLS; Conley et al 2011;Semboloni et al 2006a;Heymans et al 2012b), the ESSENCE supernova survey (Wood-Vasey et al, 2007), BAO measurements from the Sloan Digital Sky Survey (SDSS; Eisenstein et al 2005;Percival et al 2010;Padmanabhan et al 2012), and the SDSS-II supernova survey . These have been complemented by extensive multi-wavelength studies of local and high-redshift supernovae such as the Carnegie Supernova Project (Hamuy et al, 2006;Freedman et al, 2009), by systematic searches for z > 1 supernovae with Hubble Space Telescope Suzuki et al, 2012), by dark energy constraints from the evolution of X-ray or optically selected clusters (Henry et al, 2009;Vikhlinin et al, 2009;Rozo et al, 2010), by improved measurements of the Hubble constant (Riess et al, , 2011Freedman et al, 2012), and by CMB data from the WMAP satellite (Bennett et al, 2003;Larson et al, 2011) and from ground-based experiments that probe smaller angular scales.…”

Constraining thawing and freezing models with cluster number counts

“…We also use Cosmic Microwave Background (CMB) [14,15] and Large-Scale Structure (LSS) data [16,17] to help break the degeneracy between the scalar field parameters and the matter density parameter Ω m0 . For SNe Ia data, we use the publicly available latest Union2.1 compilation [13] which consists of 580 data points.…”