We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg 2 of griz imaging data from the first year of the Dark Energy Survey (DES Y1). We combine three two-point functions: (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. To demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometric redshift estimation and validation, and likelihood analysis pipelines. To prevent confirmation bias, the bulk of the analysis was carried out while "blind" to the true results; we describe an extensive suite of systematics checks performed and passed during this blinded phase. The data are modeled in flat ΛCDM and wCDM cosmologies, marginalizing over 20 nuisance parameters, varying 6 (for ΛCDM) or 7 (for wCDM) cosmological parameters including the neutrino mass density and including the 457 × 457 element analytic covariance matrix. We find consistent cosmological results from these three two-point functions, and from their combination obtain S8 ≡ σ8(Ωm/0.3) 0.5 = 0.773 +0.026 −0.020 and Ωm = 0.267 +0.030 −0.017 for ΛCDM; for wCDM, we find S8 = 0.782 +0.036 −0.024 , Ωm = 0.284 +0.033 −0.030 , and w = −0.82 +0.

We present a global measurement of the integrated Sachs-Wolfe (ISW) effect obtained by cross correlating all relevant large-scale galaxy data sets with the cosmic microwave background radiation map provided by the Wilkinson Microwave Anisotropy Probe. With these measurements, the overall ISW signal is detected at the $4:5 level. We also examine the cosmological implications of these measurements, particularly the dark energy equation of state w, its sound speed c s , and the overall curvature of the Universe. The flat ÃCDM model is a good fit to the data and, assuming this model, we find that the ISW data constrain m ¼ 0:20 þ0:19 À0:11 at the 95% confidence level. When we combine our ISW results with the latest baryon oscillation and supernovae measurements, we find that the result is still consistent with a flat ÃCDM model with w ¼ À1 out to redshifts z > 1.

Large-scale correlations in the orientations of galaxies can result from alignments in their angular momentum vectors. These alignments arise from the tidal torques exerted on neighboring protogalaxies by the smoothly varying shear Ðeld. We compute the predicted amplitude of such ellipticity correlations using the Zeldovich approximation for a realistic distribution of galaxy shapes. Weak gravitational lensing can also induce ellipticity correlations, since the images of neighboring galaxies will be distorted coherently. On comparing these two e †ects that induce shape correlations, we Ðnd that for current weaklensing surveys with a median redshift of the intrinsic signal is of the order of 1%È10% of the z m \ 1, measured signal. However, for shallower surveys with the intrinsic correlations dominate over z m ¹ 0.3, the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This di †erence can be used to disentangle these two sources of ellipticity correlations.

A flat Friedman-Roberson-Walker universe dominated by a cosmological constant (Λ) and cold dark matter (CDM) has been the working model preferred by cosmologists since the discovery of cosmic acceleration 1, 2 . However, tensions of various degrees of significance are known to be present among existing datasets within the ΛCDM framework [3][4][5][6][7][8][9][10][11] . In particular, the Lyman-α forest measurement of the Baryon Acoustic Oscillations (BAO) by the Baryon Oscillation Spectroscopic Survey (BOSS) 3 prefers a smaller value of the matter density fraction Ω M compared to the value preferred by cosmic microwave background (CMB The observational datasets considered in this work include the latest CMB temperature and polarisation anisotropy spectra, the supernovae (SNe) luminosity distance data, the BAO angular diameter distance data from the clustering of galaxies (gBAO) and from the Lyman-α forest (LyαFB), the measurement of H 0 , H(z) measurements using the relative age of old and passively evolving galaxies (OHD), the three-dimensional galaxy power spectra, and the two-dimensional weak lensing shear angular power spectra. Further details about the datasets and associated systematic effects can be found in Methods.The KL divergence, also known as relative entropy, quantifies the proximity of two probability density functions (PDFs). Rather than focusing on particular model parameters, it is designed to compare the overall concordance of datasets within a given model. We use the difference between the actual and the expected KL divergence, called "Surprise" 15 , as a measure of tension between datasets. Rather than comparing the PDFs for the ΛCDM parameters for every pair of datasets, we take the combined dataset, ALL16 (see Supplementary Fig. 1b), with the first two values signalling significant tension.Next, we check if the tension within the ΛCDM model can be interpreted as evidence for a dynamical DE. The dynamics of DE can be probed in terms of its equation of state w, which is equal to −1 for Λ, but is different in dynamical DE models where it will generally be a function of redshift z. Commonly considered alternatives to Λ are a model with a constant w (wCDM), and one in which w is linear function of the scale factor (w 0 w a CDM) 16 . We allow for a general evolution of the DE equation of state and use the correlated prior method 17 to perform a Bayesian non-parametric reconstruction of w(z) using the Monte Carlo Markov Chain method with other cosmological parameters marginalised over (see Methods for details). 0 during matter domination. Such dynamics would be consistent with our reconstruction and could be tested in the future when BAO measurements at higher redshifts become available. In addition to the reconstruction from the combined ALL16 dataset presented in Fig. 2, we present reconstructions derived from ten different data combinations in Supplementary Fig. 1.The results for tension between datasets, re-evaluated for the ALL 16 best fit w(z)CDM model, are shown with dark blue bars in F...

The fluctuations in the cosmic microwave background (CMB) have proved an invaluable tool for uncovering the nature of our universe. The recent dramatic data provided by the WMAP satellite [1] have confirmed previous indications that the expansion of the universe may be accelerating [2], driven by a cosmological constant or similar dark energy component. One consequence of dark energy is the suppression of the rate of gravitational collapse of matter at relatively recent times. This causes fluctuations in the CMB to be created as the photons pass through nearby large scale structures, a phenomenon known as the integrated Sachs-Wolfe (ISW) effect. The result is additional large scale fluctuations in the CMB which are correlated with the relatively nearby (i.e., at redshift z ∼ 1) matter distribution [3]. Here we report evidence of correlations between the WMAP data and two all sky probes of large scale structure, the hard X-ray background observed by the HEAO-1 satellite [4] and the NVSS survey of radio galaxies [5]. Both observed correlations are consistent with an ISW origin, indicating that we are seeing the impact of dark energy on the growth of structure.In the standard model of the origin of structure, most of the fluctuations were imprinted on the CMB at the epoch of last scattering, when the universe was 400,000 years old (z ≃ 1100.) The ISW effect induces extra fluctuations only when matter domination ends and the dark energy becomes important dynamically (z ∼ 1.) When this happens, the gravitational potentials of large, diffuse concentrations and rarefactions of matter begin to decay and the energy of photons passing through them changes by an amount that depends on the depth of the potentials. The amplitude of these ISW fluctuations tends to be small compared to the fluctuations originating at the epoch of last scattering except on very large scales. However, since ISW fluctuations were created more recently, it is expected that the CMB fluctuations should be partially correlated with tracers of the large scale matter distribution, e.g., with the distribution of distant galaxies.Detecting the relatively weak correlation of the CMB with the distribution of galaxies requires nearly full sky surveys out to redshifts z ∼ 1. Focus has thus has been on luminous active galaxies, which are believed to trace the mass distribution on large scales. While active galaxies emit at a wide range of frequencies, the most useful maps are in the hard X-rays (2-10 KeV), where they dominate the X-ray sky, and 1