Abstract
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 twopoint 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 galaxyshear crosscorrelation of luminous red galaxy positions and source galaxy shears. To demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometricredshift 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 twopoint functions and from their combination obtain S_{8}≡σ_{8}(Ω_{m}/0.3)^{0.5}=0.773^{+0.026}_{−0.020} and Ω_{m}=0.267^{+0.030}_{−0.017 }for ΛCDM; for wCDM, we find S_{8}=0.782^{+0.036}_{−0.024}, Ω_{m}=0.284^{+0.033}_{−0.030}, and w=−0.82^{+0.21}_{−0.20} at 68% C.L. The precision of these DES Y1 constraints rivals that from the Planck cosmic microwave background measurements, allowing a comparison of structure in the very early and late Universe on equal terms. Although the DES Y1 bestfit values for S_{8 }and Ω_{m }are lower than the central values from Planck for both
ΛCDM and wCDM, the Bayes factor indicates that the DES Y1 and Planck data sets are consistent with each other in the context of ΛCDM. Combining DES Y1 with Planck, baryonic acoustic oscillation measurements from SDSS, 6dF, and BOSS and type Ia supernovae from the Joint Lightcurve Analysis data set, we derive very tight constraints on cosmological parameters: S_{8 }= 0.802 ± 0.012 and Ω_{m}= 0.298 ± 0.007 in ΛCDM and w=−1.00^{+0.05}_{−0.04 }in wCDM. Upcoming Dark Energy Survey analyses will provide more stringent tests of the ΛCDM
model and extensions such as a timevarying equation of state of dark energy or modified gravity.
element analytic covariance matrix. We find consistent cosmological results from these three twopoint functions and from their combination obtain S_{8}≡σ_{8}(Ω_{m}/0.3)^{0.5}=0.773^{+0.026}_{−0.020} and Ω_{m}=0.267^{+0.030}_{−0.017 }for ΛCDM; for wCDM, we find S_{8}=0.782^{+0.036}_{−0.024}, Ω_{m}=0.284^{+0.033}_{−0.030}, and w=−0.82^{+0.21}_{−0.20} at 68% C.L. The precision of these DES Y1 constraints rivals that from the Planck cosmic microwave background measurements, allowing a comparison of structure in the very early and late Universe on equal terms. Although the DES Y1 bestfit values for S_{8 }and Ω_{m }are lower than the central values from Planck for both
ΛCDM and wCDM, the Bayes factor indicates that the DES Y1 and Planck data sets are consistent with each other in the context of ΛCDM. Combining DES Y1 with Planck, baryonic acoustic oscillation measurements from SDSS, 6dF, and BOSS and type Ia supernovae from the Joint Lightcurve Analysis data set, we derive very tight constraints on cosmological parameters: S_{8 }= 0.802 ± 0.012 and Ω_{m}= 0.298 ± 0.007 in ΛCDM and w=−1.00^{+0.05}_{−0.04 }in wCDM. Upcoming Dark Energy Survey analyses will provide more stringent tests of the ΛCDM
model and extensions such as a timevarying equation of state of dark energy or modified gravity.
Original language  English 

Article number  043526 
Number of pages  31 
Journal  Physical Review D, particles, fields, gravitation, and cosmology 
Volume  98 
Issue number  4 
DOIs  
Publication status  Published  27 Aug 2018 
Keywords
 Astrophysics  Cosmology and Nongalactic Astrophysics
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Joe Zuntz
 School of Physics and Astronomy  Reader and Chancellor's Fellow
Person: Academic: Research Active