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We study the clustering of galaxies detected at i < 22.5 in the Science Verification observations of the Dark Energy Survey (DES). Two-point correlation functions are measured using 2.3×106 galaxies over a contiguous 116 deg2 region in five bins of photometric redshift width Δz = 0.2 in the range 0.2 < z < 1.2. The impact of photometric redshift errors is assessed by comparing results using a template-based photo-z algorithm (BPZ) to a machine-learning algorithm (TPZ). A companion paper presents maps of several observational variables (e.g. seeing, sky brightness) which could modulate the galaxy density. Here we characterize and mitigate systematic errors on the measured clustering which arise from these observational variables, in addition to others such as Galactic dust and stellar contamination. After correcting for systematic effects, we measure galaxy bias over a broad range of linear scales relative to mass clustering predicted from the Planck Λ cold dark matter model, finding agreement with the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) measurements with χ2 of 4.0 (8.7) with 5 degrees of freedom for the TPZ (BPZ) redshifts. We test a 'linear bias' model, in which the galaxy clustering is a fixed multiple of the predicted non-linear dark matter clustering. The precision of the data allows us to determine that the linear bias model describes the observed galaxy clustering to 2.5 per cent accuracy down to scales at least 4-10 times smaller than those on which linear theory is expected to be sufficient.

We present the first quantitative detection of large-scale filamentary structure at z ≃ 0.7 in the large cosmological volume probed by the VIMOS Public Extragalactic Redshift Survey (VIPERS).We use simulations to show the capability of VIPERS to recover robust topological features in the galaxy distribution, in particular the filamentary network. We then investigate how galaxies with different stellar masses and stellar activities are distributed around the filaments, and find a significant segregation, with the most massive or quiescent galaxies being closer to the filament axis than less massive or active galaxies. The signal persists even after downweighting the contribution of peak regions. Our results suggest that massive and quiescent galaxies assemble their stellar mass through successive mergers during their migration along filaments towards the nodes of the cosmic web. On the other hand, low-mass star-forming galaxies prefer the outer edge of filaments, a vorticity-rich region dominated by smooth accretion, as predicted by the recent spin alignment theory. This emphasizes the role of large-scale cosmic flows in shaping galaxy properties. [ABSTRACT FROM AUTHOR]

We present a re-analysis of the CFHTLenS weak gravitational lensing survey using Complete Orthogonal Sets of E/B-mode Integrals, known as COSEBIs. COSEBIs provide a complete set of functions to efficiently separate E-modes from B-modes and hence allow for robust and stringent tests for systematic errors in the data. This analysis reveals significant B-modes on large angular scales that were not previously seen using the standard E/B decomposition analyses. We find that the significance of the B-modes is enhanced when the data are split by galaxy type and analysed in tomographic redshift bins. Adding tomographic bins to the analysis increases the number of COSEBIs modes, which results in a less-accurate estimation of the covariance matrix from a set of simulations. We therefore also present the first compressed COSEBIs analysis of survey data, where the COSEBIs modes are optimally combined based on their sensitivity to cosmological parameters. In this tomographic CCOSEBIs analysis, we find the B-modes to be consistent with zero when the full range of angular scales are considered. [ABSTRACT FROM AUTHOR]

The VLT Survey Telescope ATLAS survey is an optical ugriz survey aiming to cover 4700 deg² of the southern sky to similar depths as the Sloan Digital Sky Survey (SDSS). From reduced images and object catalogues provided by the Cambridge Astronomical Surveys Unit, we first find that the median seeing ranges from 0.8 arcsec FWHM (full width at halfmaximum) in i to 1.0 arcsec in u, significantly better than the 1.2-1.5 arcsec seeing for SDSS. The 5s mag limit for stellar sources is rAB = 22.7 and in all bands these limits are at least as faint as SDSS. SDSS and ATLAS are more equivalent for galaxy photometry except in the z band where ATLAS has significantly higher throughput. We have improved the original ESO magnitude zero-points by comparing m < 16 star magnitudes with the AAVSO Photometric All-Sky Survey in gri, also extrapolating into u and z, resulting in zero-points accurate to ±0.02 mag. We finally compare star and galaxy number counts in a 250 deg² area with SDSS and other count data and find good agreement. ATLAS data products can be retrieved from the ESO Science Archive, while support for survey science analyses is provided by the OmegaCAM Science Archive, operated by the Wide-Field Astronomy Unit in Edinburgh. [ABSTRACT FROM AUTHOR]

The stacked density profile of cosmic voids in the galaxy distribution provides an important tool for the use of voids for precision cosmology. We study the density profiles of voids identified using the ZOBOV watershed transform algorithm in realistic mock luminous red galaxy (LRG) catalogues from the Jubilee simulation, as well as in void catalogues constructed from the SDSS LRG and Main Galaxy samples. We compare different methods for reconstructing density profiles scaled by the void radius and show that the most commonly used method based on counts in shells and simple averaging is statistically flawed as it underestimates the density in void interiors. We provide two alternative methods that do not suffer from this effect; one based on Voronoi tessellations is also easily able to account from artefacts due to finite survey boundaries and so is more suitable when comparing simulation data to observation. Using this method, we show that the most robust voids in simulation are exactly self-similar, meaning that their average rescaled profile does not depend on the void size. Within the range of our simulation, we also find no redshift dependence of the mean profile. Comparison of the profiles obtained from simulated and real voids shows an excellent match. The mean profiles of real voids also show a universal behaviour over a wide range of galaxy luminosities, number densities and redshifts. This points to a fundamental property of the voids found by the watershed algorithm, which can be exploited in future studies of voids. [ABSTRACT FROM AUTHOR]

Constraints on cosmology from recent cosmic shear observations are becoming increasingly sophisticated in their treatment of potential systematic effects. Here we present cosmological constraints which include modelling of intrinsic alignments. We demonstrate how the results are changed for three different intrinsic alignment models, and for two different models of the cosmic shear galaxy population. We find that intrinsic alignments can either reduce or increase measurements of the fluctuation amplitude parameter σ depending on these decisions, and depending on the cosmic shear survey properties. This is due to the interplay between the two types of intrinsic alignment, intrinsic-intrinsic (II) and gravitational-intrinsic (GI). It has been shown that future surveys must make a careful treatment of intrinsic alignments to avoid significant biases, and that simultaneous constraints from shear-shear and shear-position correlation functions can mitigate the effects. For the first time we here combine constraints from cosmic shear surveys (shear-shear correlations) with those from 'GI' intrinsic alignment data sets (shear-position correlations). We produce updated constraints on cosmology marginalized over two free parameters in the halo model for intrinsic alignments. We find that the additional freedom is well compensated by the additional information, in that the constraints are very similar indeed to those obtained when intrinsic alignments are ignored, in terms of both best-fitting values and uncertainties. [ABSTRACT FROM AUTHOR]

We develop an optimized technique to extract density–density and velocity–velocity spectra out of observed spectra in redshift space. The measured spectra of the distribution of haloes from redshift distorted mock map are binned into two-dimensional coordinates in Fourier space so as to be decomposed into both spectra using angular projection dependence. With the threshold limit introduced to minimize non-linear suppression, the decomposed velocity–velocity spectra are reasonably well measured up to scale , and the measured variances using our method are consistent with errors predicted from a Fisher matrix analysis. The detectability is extendable to with more conservative bounds at the cost of weakened constraint. [ABSTRACT FROM AUTHOR]

We study the 3D distribution of matter at using high-resolution spectra of quasi-stellar object (QSO) pairs and simulated spectra drawn from cosmological hydrodynamical simulations. We present a sample of 15 QSOs, corresponding to 21 baselines of angular separations evenly distributed between ∼1 and 14 arcmin, observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory Very Large Telescope (ESO–VLT). The observed correlation functions of the transmitted flux in the H i Lyman α forest transverse to and along the line of sight are in agreement, implying that the distortions in redshift space due to peculiar velocities are relatively small and – within the relatively large error bars – not significant. The clustering signal is significant up to velocity separations of ∼300 km s−1, corresponding to about comoving Mpc. Compatibility at the 2σ level has been found both for the autocorrelation and cross-correlation functions and for the set of the cross-correlation coefficients. The analysis focuses in particular on two QSO groups of the sample, the Sextet and the Triplet. Searching for alignments in the redshift space between Lyman α absorption lines belonging to different lines of sight, it has been possible to discover the presence of a wide H i structure extending over about 10 Mpc in comoving space, and give constraints on the sizes of two cosmic underdense regions in the intergalactic medium, which have been detected with a 91 and 86 per cent significance level, respectively, in the Sextet and the Triplet. [ABSTRACT FROM AUTHOR]

We describe an exact, flexible and computationally efficient algorithm for a joint inference of the large-scale structure and its power spectrum, building on a Gibbs sampling framework and present its implementationares (Algorithm for REconstruction and Sampling).ares is designed to reconstruct the 3D power spectrum together with the underlying dark matter density field in a Bayesian framework, under the reasonable assumption that the long-wavelength Fourier components are Gaussian distributed. As a resultares does not only provide a single estimate but samples from the joint posterior of the power spectrum and density field conditional on a set of observations. This enables us to calculate any desired statistical summary, in particular we are able to provide joint uncertainty information. We apply our method to mock catalogues, with highly structured observational masks and selection functions, in order to demonstrate its ability to infer the power spectrum from real data sets, while fully accounting for any mask induced mode coupling. [ABSTRACT FROM AUTHOR]

In a flat universe dominated by dark energy, the integrated Sachs–Wolfe (ISW) effect can be detected as a large-angle cross-correlation between the cosmic microwave background and a tracer of large-scale structure. We investigate whether the inconclusive ISW signal derived from Two-Micron All-Sky Survey (2MASS) galaxy maps can be improved upon by including photometric redshifts for the 2MASS galaxies. These redshifts are derived by matching the 2MASS data with optical catalogues generated from SuperCOSMOS scans of major photographic sky surveys. We find no significant ISW signal in this analysis; an ISW effect of the form expected in a Λ cold dark matter universe is only weakly preferred over no correlation, with a likelihood ratio of 1.5:1. We consider ISW detection prospects for future large-scale structure surveys with fainter magnitude limits and greater survey depth; even with the best possible data, the ISW cross-correlation signal would be expected to evade detection in ≳10 per cent of cases. [ABSTRACT FROM AUTHOR]

We estimate the local density field in redshift shells to a maximum redshift of , using photometric redshifts for the Two-Micron All-Sky Survey galaxy catalogue, matched to optical data from the SuperCOSMOS galaxy catalogue. This density-field map is used to predict the integrated Sachs–Wolfe (ISW) cosmic microwave background (CMB) anisotropies that originate within the volume at . We investigate the impact of this estimated ISW foreground signal on large-scale anomalies in the Wilkinson Microwave Anisotropy Probe (WMAP) CMB data. We find that removal of the foreground ISW signal from WMAP data reduces the significance of a number of reported large-scale anomalies in the CMB, including the low quadrupole power and the apparent alignment between the CMB quadrupole and octopole. [ABSTRACT FROM AUTHOR]

We investigate the topology of the completed 2dF Galaxy Redshift Survey (2dFGRS), drawing two flux-limited samples of the local Universe from the 2dFGRS catalogue, which contains over 220 000 galaxies at a median redshift of . The samples are cut at and corrected for selection effects. We then use the three-dimensional genus statistic to probe the connectedness of the galaxy distribution on scales ranging from 8 to 20 Mpc, and compare these measurements with the analytical result for a Gaussian random density field, a generic prediction of inflationary models. We demonstrate consistency with inflation on the range of scales considered. We then introduce a parametrization of the analytic genus curve formula that is sensitive to asymmetries in genus number as a function of density and use it to demonstrate that such phenomena are ruled out with 95 per cent confidence between 8 and 16 Mpc. [ABSTRACT FROM AUTHOR]

We report on measurements of the cosmological constant, Λ, and the redshift space distortion parameter , based on an analysis of the quasi-stellar object (QSO) power spectrum parallel and perpendicular to the observer's line of sight, , from the final catalogue of the Two-Degree Field (2dF) QSO Redshift Survey. We derive a joint constraint from the geometric and redshift-space distortions in the power spectrum. By combining this result with a second constraint based on mass clustering evolution, we break this degeneracy and obtain strong constraints on both parameters. Assuming a flat cosmology and a Λ cosmology r( z) function to convert from redshift into comoving distance, we find best-fitting values of and . Assuming instead an Einstein–de Sitter cosmology r( z) we find that the best-fitting model obtained, with and , is consistent with the Λ r( z) results, and inconsistent with a flat cosmology at over 95 per cent confidence. [ABSTRACT FROM AUTHOR]

We report on measurements of the cosmological constant, Λ, and the redshift space distortion parameter , based on an analysis of the quasi-stellar object (QSO) power spectrum parallel and perpendicular to the observer's line of sight, , from the final catalogue of the Two-Degree Field (2dF) QSO Redshift Survey. We derive a joint constraint from the geometric and redshift-space distortions in the power spectrum. By combining this result with a second constraint based on mass clustering evolution, we break this degeneracy and obtain strong constraints on both parameters. Assuming a flat cosmology and a Λ cosmology r( z) function to convert from redshift into comoving distance, we find best-fitting values of and . Assuming instead an Einstein–de Sitter cosmology r( z) we find that the best-fitting model obtained, with and , is consistent with the Λ r( z) results, and inconsistent with a flat cosmology at over 95 per cent confidence. [ABSTRACT FROM AUTHOR]

We use the Two-Degree Field Galaxy Redshift Survey (2dFGRS) to test the hierarchical scaling hypothesis: namely, that the p-point galaxy correlation functions can be written in terms of the two-point correlation function or variance. This scaling is expected if an initially Gaussian distribution of density fluctuations evolves under the action of gravitational instability. We measure the volume-averaged p-point correlation functions using a counts-in-cells technique applied to a volume-limited sample of 44 931 L* galaxies. We demonstrate that L* galaxies display hierarchical clustering up to order in redshift space. The variance measured for L* galaxies is in excellent agreement with the predictions from a Λ-cold dark matter N-body simulation. This applies to all cell radii considered, . However, the higher order correlation functions of L* galaxies have a significantly smaller amplitude than is predicted for the dark matter for . This disagreement implies that a non-linear bias exists between the dark matter and L* galaxies on these scales. We also show that the presence of two rare, massive superclusters in the 2dFGRS has an impact on the higher-order clustering moments measured on large scales. [ABSTRACT FROM AUTHOR]