Dark Energy Survey Year 1 results: the impact of galaxy neighbours on weak lensing cosmology with im3shape

588

564

We use 26 × 10 6 galaxies from the Dark Energy Survey (DES) Year 1 shape catalogs over 1321 deg 2 of the sky to produce the most significant measurement of cosmic shear in a galaxy survey to date. We constrain cosmological parameters in both the flat ΛCDM and the wCDM models, while also varying the neutrino mass density. These results are shown to be robust using two independent shape catalogs, two independent photo-z calibration methods, and two independent analysis pipelines in a blind analysis. We find a 3.5% fractional uncertainty on σ 8 ðΩ m =0.3Þ 0.5 ¼ 0.782 −0.39 . We find results that are consistent with previous cosmic shear constraints in σ 8 -Ω m , and we see no evidence for disagreement of our weak lensing data with data from the cosmic microwave background. Finally, we find no evidence preferring a wCDM model allowing w ≠ −1. We expect further significant improvements with subsequent years of DES data, which will more than triple the sky coverage of our shape catalogs and double the effective integrated exposure time per galaxy.

Section: Im3shapementioning

confidence: 99%

“…(iii) Shape measurement, calibration techniques, and validation of the two shape catalogs, METACALIBRATION and IM3SHAPE, are described in [40]. (iv) Further exploration of the IM3SHAPE image simulations is discussed in [56]. (v) Additional null tests of the reconstructed shear or convergence fields are discussed in [57].…”

Section: Introductionmentioning

confidence: 99%

Dark Energy Survey Year 1 results: Cosmological constraints from cosmic shear

Troxel¹,

MacCrann²,

Zuntz³

et al. 2018

588

564

“…Multiplicative biases in these estimators are calibrated using realistic images simulations of DES Y1 [34,42].…”

Section: Lensing Source Catalogsmentioning

confidence: 99%

Density split statistics: Cosmological constraints from counts and lensing in cells in DES Y1 and SDSS data

Gruen¹,

Friedrich²,

Krause³

et al. 2018

113

114

We derive cosmological constraints from the probability distribution function (PDF) of evolved large-scale matter density fluctuations. We do this by splitting lines of sight by density based on their count of tracer galaxies, and by measuring both gravitational shear around and counts-in-cells in overdense and underdense lines of sight, in Dark Energy Survey (DES) First Year and Sloan Digital Sky Survey (SDSS) data. Our analysis uses a perturbation theory model [O. Friedrich et al., Phys. Rev. D 98, 023508 (2018)] and is validated using N-body simulation realizations and log-normal mocks. It allows us to constrain cosmology, bias and stochasticity of galaxies with respect to matter density and, in addition, the skewness of the matter density field. From a Bayesian model comparison, we find that the data weakly prefer a connection of galaxies and matter that is stochastic beyond Poisson fluctuations on ≤ 20 arcmin angular smoothing scale. The two stochasticity models we fit yield DES constraints on the matter density Ω m ¼ 0.26 −0.07 for the two stochasticity models), but consistent with each other and with the 3 x 2pt results if stochasticity is at the low end of the posterior range. As an additional test of gravity, counts and lensing in cells allow to compare the skewness S 3 of the matter density PDF to its ΛCDM prediction. We find no evidence of excess skewness in any model or data set, with better than 25 per cent relative precision in the skewness estimate from DES alone.

“…It performs a maximum likelihood fit using a bulge-or-disk galaxy model to estimate the ellipticity of a galaxy, i.e., it fits de Vaucouleurs bulge and exponential disk components to galaxy images in the r band, with shear biases calibrated from realistic simulations [45,48].…”

Section: B Source Samples: Metacalibration and Im3shapementioning

confidence: 99%

Dark Energy Survey year 1 results: Galaxy-galaxy lensing

Prat¹,

Sánchez²,

Fang³

et al. 2018

106

We present galaxy-galaxy lensing measurements from 1321 sq. deg. of the Dark Energy Survey (DES) Year 1 (Y1) data. The lens sample consists of a selection of 660,000 red galaxies with high-precision photometric redshifts, known as redMaGiC, split into five tomographic bins in the redshift range 0.15 < z < 0.9. We use two different source samples, obtained from the METACALIBRATION (26 million galaxies) and IM3SHAPE (18 million galaxies) shear estimation codes, which are split into four photometric redshift bins in the range 0.2 < z < 1.3. We perform extensive testing of potential systematic effects that can bias the galaxy-galaxy lensing signal, including those from shear estimation, photometric redshifts, and * Corresponding author. jprat@ifae.es † Corresponding author. csanchez@ifae.es J. PRAT et al. PHYS. REV. D 98, 042005 (2018) 042005-2 observational properties. Covariances are obtained from jackknife subsamples of the data and validated with a suite of log-normal simulations. We use the shear-ratio geometric test to obtain independent constraints on the mean of the source redshift distributions, providing validation of those obtained from other photo-z studies with the same data. We find consistency between the galaxy bias estimates obtained from our galaxy-galaxy lensing measurements and from galaxy clustering, therefore showing the galaxymatter cross-correlation coefficient r to be consistent with one, measured over the scales used for the cosmological analysis. The results in this work present one of the three two-point correlation functions, along with galaxy clustering and cosmic shear, used in the DES cosmological analysis of Y1 data, and hence the methodology and the systematics tests presented here provide a critical input for that study as well as for future cosmological analyses in DES and other photometric galaxy surveys.