Daniel Margala

Baryon acoustic oscillations in the Lyα forest of BOSS DR11 quasars

We report a detection of the baryon acoustic oscillation (BAO) feature in the flux-correlation function of the Ly forest of high-redshift quasars with a statistical significance of five standard deviations. The study uses 137,562 quasars in the redshift range 2:1 z 3:5 from the Data Release 11 (DR11) of the Baryon Oscillation Spectroscopic Survey (BOSS) of SDSS-III. This sample contains three times the number of quasars used in previous studies. The measured position of the BAO peak determines the angular distance, DA(z = 2:34) and expansion rate, H(z = 2:34), both on a scale set by the sound horizon at the drag epoch, rd. We find DA=rd =

Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

Author(s): Font-Ribera, A; Kirkby, D; Busca, N; Miralda-Escude, J; Ross, NP; Slosar, A; Rich, J; Aubourg, E; Bailey, S; Bhardwaj, V; Bautista, J; Beutler, F; Bizyaev, D; Blomqvist, M; Brewington, H; Brinkmann, J; Brownstein, JR; Carithers, B; Dawson, KS; Delubac, T; Ebelke, G; Eisenstein, DJ; Ge, J; Kinemuchi, K; Lee, KG; Malanushenko, V; Malanushenko, E; Marchante, M; Margala, D; Muna, D; Myers, AD; Noterdaeme, P; Oravetz, D; Palanque-Delabrouille, N; Pâris, I; Petitjean, P; Pieri, MM; Rossi, G; Schneider, DP; Simmons, A; Viel, M; Yeche, C; York, DG | Abstract: We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c/(H(z = 2.36)rs) = 9.0±0.3 and across the line of sight DA (z = 2.36)/rs = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (rs = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s -1 Mpc-1 and of the angular diameter distance of D A (z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.©2014 IOP Publishing Ltd and Sissa Medialab srl.

Measurement of baryon acoustic oscillations in the Lyman-α forest fluctuations in BOSS data release 9

We use the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 9 (DR9) to detect and measure the position of the Baryonic Acoustic Oscillation (BAO) feature in the three-dimensional correlation function in the Lyman-α flux fluctuations at a redshift zeff = 2.4. The feature is clearly detected at significance between 3 and 5 sigma (depending on the broadband model and method of error covariance matrix estimation) and is consistent with predictions of the standard ΛCDM model. We assess the biases in our method, stability of the error covariance matrix and possible systematic effects. We fit the resulting correlation function with several models that decouple the broadband and acoustic scale information. For an isotropic dilation factor, we measure 100 × (αiso − 1) = −1.6+2.0 +4.3 +7.4−2.0 −4.1 −6.8 (stat.) ±1.0 (syst.) (multiple statistical errors denote 1,2 and 3 sigma confidence limits) with respect to the acoustic scale in the fiducial cosmological model (flat ΛCDM with Ωm = 0.27, h = 0.7). When fitting separately for the radial and transversal dilation factors we find marginalised constraints 100 × (α|| − 1) = −1.3+3.5 +7.6 +12.3−3.3 −6.7 −10.2 (stat.) ±2.0 (syst.) and 100 × (α⊥ − 1) = −2.2+7.4 +17−7.1 −15 (stat.) ±3.0 (syst.). The dilation factor measurements are significantly correlated with cross-correlation coefficient of ~ −0.55. Errors become significantly non-Gaussian for deviations over 3 standard deviations from best fit value. Because of the data cuts and analysis method, these measurements give tighter constraints than a previous BAO analysis of the BOSS DR9 Lyman-α sample, providing an important consistency test of the standard cosmological model in a new redshift regime.

Image analysis for cosmology: results from the GREAT10 Galaxy Challenge

We present the results from the first public blind point-spread function (PSF) reconstruction challenge, the GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Star Challenge. Reconstruction of a spatially varying PSF, sparsely sampled by stars, at non-star positions is a critical part in the image analysis for weak lensing where inaccuracies in the modeled ellipticity e and size R^2 can impact the ability to measure the shapes of galaxies. This is of importance because weak lensing is a particularly sensitive probe of dark energy and can be used to map the mass distribution of large scale structure. Participants in the challenge were presented with 27,500 stars over 1300 images subdivided into 26 sets, where in each set a category change was made in the type or spatial variation of the PSF. Thirty submissions were made by nine teams. The best methods reconstructed the PSF with an accuracy of σ(e) ≈ 2.5 × 10^(–4) and σ(R^2)/R^2 ≈ 7.4 × 10^(–4). For a fixed pixel scale, narrower PSFs were found to be more difficult to model than larger PSFs, and the PSF reconstruction was severely degraded with the inclusion of an atmospheric turbulence model (although this result is likely to be a strong function of the amplitude of the turbulence power spectrum).

Baryon Acoustic Oscillations in the Ly-α forest of BOSS quasars

We report a detection of the baryon acoustic oscillation (BAO) feature in the three-dimensional correlation function of the transmitted flux fraction in the \Lya forest of high-redshift quasars. The study uses 48,640 quasars in the redshift range

THE THIRD GRAVITATIONAL LENSING ACCURACY TESTING (GREAT3) CHALLENGE HANDBOOK

2.1\le z \le 3.5

THE BOSS Lyα FOREST SAMPLE FROM SDSS DATA RELEASE 9

from the Baryon Oscillation Spectroscopic Survey (BOSS) of the third generation of the Sloan Digital Sky Survey (SDSS-III). At a mean redshift

THE BOSS Ly{alpha} FOREST SAMPLE FROM SDSS DATA RELEASE 9

z=2.3

Fitting methods for baryon acoustic oscillations in the Lyman-α forest fluctuations in BOSS data release 9

, we measure the monopole and quadrupole components of the correlation function for separations in the range

IMPROVED SPECTROPHOTOMETRIC CALIBRATION OF THE SDSS-III BOSS QUASAR SAMPLE

20\hMpc<r<200\hMpc