A 2 per cent distance toz= 0.35 by reconstructing baryon acoustic oscillations – I. Methods and application to the Sloan Digital Sky Survey

Abstract

We present the first application to density field reconstruction to a galaxy survey to undo the smoothing of the baryon acoustic oscillation (BAO) feature due to non-linear gravitational evolution and thereby improve the precision of the distance measurements possible. We apply the reconstruction technique to the clustering of galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) luminous red galaxy (LRG) sample, sharpening the BAO feature and achieving a 1.9 per cent measurement of the distance to z = 0.35. We update the reconstruction algorithm of Eisenstein et al. to account for the effects of survey geometry as well as redshift-space distortions and validate it on 160 LasDamas simulations. We demonstrate that reconstruction sharpens the BAO feature in the angle averaged galaxy correlation function, reducing the non-linear smoothing scale nl from 8.1 to 4.4 Mpc h −1 . Reconstruction also significantly reduces the effects of redshift-space distortions at the BAO scale, isotropizing the correlation function. This sharpened BAO feature yields an unbiased distance estimate (<0.2 per cent) and reduces the scatter from 3.3 to 2.1 per cent. We demonstrate the robustness of these results to the various reconstruction parameters, including the smoothing scale, the galaxy bias and the linear growth rate. Applying this reconstruction algorithm to the SDSS LRG DR7 sample improves the significance of the BAO feature in these data from 3.3σ for the unreconstructed correlation function to 4.2σ after reconstruction. We estimate a relative distance scale D V /r s to z = 0.35 of 8.88 ± 0.17, where r s is the sound horizon and D V ≡ (D 2 A H −1 ) 1/3 is a combination of the angular diameter distance D A and Hubble parameter H. Assuming a sound horizon of 154.25 Mpc, this translates into a distance measurement D V (z = 0.35) = 1.356 ± 0.025 Gpc. We find that reconstruction reduces the distance error in the DR7 sample from 3.5 to 1.9 per cent, equivalent to a survey with three times the volume of SDSS.

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]. In Fig.…”

“…We are using the results from Padmanabhan et al [13], which reported a measure- We combine theses results with the Planck 2015 [17] values 100θ * = 1.04106 ± 0.00031, which gives l A = π/θ * = 301.77 ± 0.09, r s (z d ) = 147.41 ± 0.30 and r s (z * ) = 144.71 ± 0.31, for the combined analysis TT, TE, EE+lowP+lensing (see Table 4 of that reference). Following [32], we multiply the value of r s (z d ) by a constant factor of 1.0275 to take into account the difference between CAMB [33] results and the Eisenstein and Hu approximation [34] used in the BAO analysis.…”

“…We use the following datasets: a) observations of type Ia supernovae from the Joint Lightcurve Analysis (JLA) of the Sloan Digital Sky Survey (SDSS-II) and the Supernova Legacy Survey (SNLS) samples [12]; b) observations of baryon acoustic oscillations in the SDSS DR7 [13] and SDSS DR9 [14], in the WiggleZ Survey [15] and in the 6dF Galaxy Survey (6dFGRS) [16]; c) measurements of cosmic microwave background temperature anisotropy from 2015 Planck [17] and WMAP9-year [18]; d) observations of the Hubble rate H(z) from [19][20][21][22][23][24]. In the following subsections, the statistical analysis used to deal with those observables is briefly described.…”

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.…”

Large-scale structure observations

“…Beutler et al 2011;Blake et al 2011;Padmanabhan et al 2012), leading to the analyses presented in (Anderson et al 2012). Since then, the DR9 data set has been analysed splitting into measurements along and across the line-of-sight , and the next release of measurements from BOSS is imminent.…”