scholarly journals Dark Energy Survey Year 3 results: cosmology with moments of weak lensing mass maps – validation on simulations

2020 ◽  
Vol 498 (3) ◽  
pp. 4060-4087
Author(s):  
M Gatti ◽  
C Chang ◽  
O Friedrich ◽  
B Jain ◽  
D Bacon ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Weak Lensing ◽  
Subsequent Paper ◽  
The Third ◽  
Dark Energy Survey ◽  
Simulated Likelihood ◽  
Modelling Uncertainties ◽  
Non Gaussian ◽  
Energy Survey

ABSTRACT We present a simulated cosmology analysis using the second and third moments of the weak lensing mass (convergence) maps. The second moment, or variances, of the convergence as a function of smoothing scale contains information similar to standard shear two-point statistics. The third moment, or the skewness, contains additional non-Gaussian information. The analysis is geared towards the third year (Y3) data from the Dark Energy Survey (DES), but the methodology can be applied to other weak lensing data sets. We present the formalism for obtaining the convergence maps from the measured shear and for obtaining the second and third moments of these maps given partial sky coverage. We estimate the covariance matrix from a large suite of numerical simulations. We test our pipeline through a simulated likelihood analyses varying 5 cosmological parameters and 10 nuisance parameters and identify the scales where systematic or modelling uncertainties are not expected to affect the cosmological analysis. Our simulated likelihood analysis shows that the combination of second and third moments provides a 1.5 per cent constraint on S8 ≡ σ8(Ωm/0.3)0.5 for DES Year 3 data. This is 20 per cent better than an analysis using a simulated DES Y3 shear two-point statistics, owing to the non-Gaussian information captured by the inclusion of higher order statistics. This paper validates our methodology for constraining cosmology with DES Year 3 data, which will be presented in a subsequent paper.

scholarly journals Likelihood-free inference with neural compression of DES SV weak lensing map statistics

2020 ◽  
Vol 501 (1) ◽  
pp. 954-969
Author(s):  
Niall Jeffrey ◽  
Justin Alsing ◽  
François Lanusse
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Power Spectra ◽  
Weak Lensing ◽  
Probability Density Estimation ◽  
Unknown Parameters ◽  
Dark Energy Survey ◽  
Inference Problems ◽  
Energy Survey

ABSTRACT In many cosmological inference problems, the likelihood (the probability of the observed data as a function of the unknown parameters) is unknown or intractable. This necessitates approximations and assumptions, which can lead to incorrect inference of cosmological parameters, including the nature of dark matter and dark energy, or create artificial model tensions. Likelihood-free inference covers a novel family of methods to rigorously estimate posterior distributions of parameters using forward modelling of mock data. We present likelihood-free cosmological parameter inference using weak lensing maps from the Dark Energy Survey (DES) Science Verification data, using neural data compression of weak lensing map summary statistics. We explore combinations of the power spectra, peak counts, and neural compressed summaries of the lensing mass map using deep convolution neural networks. We demonstrate methods to validate the inference process, for both the data modelling and the probability density estimation steps. Likelihood-free inference provides a robust and scalable alternative for rigorous large-scale cosmological inference with galaxy survey data (for DES, Euclid, and LSST). We have made our simulated lensing maps publicly available.

scholarly journals Weak-lensing analysis of SPT-selected galaxy clusters using Dark Energy Survey Science Verification data

2019 ◽  
Vol 485 (1) ◽  
pp. 69-87 ◽  
Author(s):  
C Stern ◽  
J P Dietrich ◽  
S Bocquet ◽  
D Applegate ◽  
J J Mohr ◽  
...  
Keyword(s):  
Dark Energy ◽  
Galaxy Clusters ◽  
Weak Lensing ◽  
Dark Energy Survey ◽  
Energy Survey

scholarly journals Dark Energy Survey Year 1 Results: Cosmological constraints from cluster abundances and weak lensing

2020 ◽  
Vol 102 (2) ◽  
Author(s):  
T. M. C. Abbott ◽  
M. Aguena ◽  
A. Alarcon ◽  
S. Allam ◽  
S. Allen ◽  
...  
Keyword(s):  
Dark Energy ◽  
Weak Lensing ◽  
Cosmological Constraints ◽  
Dark Energy Survey ◽  
Energy Survey

scholarly journals Dark Energy Survey Year 1 Results: redshift distributions of the weak-lensing source galaxies

2018 ◽  
Vol 478 (1) ◽  
pp. 592-610 ◽  
Author(s):  
B Hoyle ◽  
D Gruen ◽  
G M Bernstein ◽  
M M Rau ◽  
J De Vicente ◽  
...  
Keyword(s):  
Dark Energy ◽  
Weak Lensing ◽  
Dark Energy Survey ◽  
Energy Survey

scholarly journals Studying Type II supernovae as cosmological standard candles using the Dark Energy Survey

2020 ◽  
Vol 495 (4) ◽  
pp. 4860-4892 ◽  
Author(s):  
T de Jaeger ◽  
L Galbany ◽  
S González-Gaitán ◽  
R Kessler ◽  
A V Filippenko ◽  
...  
Keyword(s):  
Dark Energy ◽  
High Redshift ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Distance Modulus ◽  
Type Ii ◽  
Hubble Diagram ◽  
Dark Energy Survey ◽  
Spectroscopic Information ◽  
Energy Survey

ABSTRACT Despite vast improvements in the measurement of the cosmological parameters, the nature of dark energy and an accurate value of the Hubble constant (H0) in the Hubble–Lemaître law remain unknown. To break the current impasse, it is necessary to develop as many independent techniques as possible, such as the use of Type II supernovae (SNe II). The goal of this paper is to demonstrate the utility of SNe II for deriving accurate extragalactic distances, which will be an asset for the next generation of telescopes where more-distant SNe II will be discovered. More specifically, we present a sample from the Dark Energy Survey Supernova Program (DES-SN) consisting of 15 SNe II with photometric and spectroscopic information spanning a redshift range up to 0.35. Combining our DES SNe with publicly available samples, and using the standard candle method (SCM), we construct the largest available Hubble diagram with SNe II in the Hubble flow (70 SNe II) and find an observed dispersion of 0.27 mag. We demonstrate that adding a colour term to the SN II standardization does not reduce the scatter in the Hubble diagram. Although SNe II are viable as distance indicators, this work points out important issues for improving their utility as independent extragalactic beacons: find new correlations, define a more standard subclass of SNe II, construct new SN II templates, and dedicate more observing time to high-redshift SNe II. Finally, for the first time, we perform simulations to estimate the redshift-dependent distance-modulus bias due to selection effects.

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

2017 ◽  
Vol 475 (4) ◽  
pp. 4524-4543 ◽  
Author(s):  
S Samuroff ◽  
S L Bridle ◽  
J Zuntz ◽  
M A Troxel ◽  
D Gruen ◽  
...  
Keyword(s):  
Dark Energy ◽  
Weak Lensing ◽  
Dark Energy Survey ◽  
The Impact ◽  
Energy Survey

scholarly journals Cosmic Bayes. Datasets and priors in the hunt for dark energy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michela Massimi
Keyword(s):  
Parameter Estimation ◽  
Dark Energy ◽  
Model Selection ◽  
Bayesian Methods ◽  
Cosmological Parameters ◽  
Observational Cosmology ◽  
Dark Energy Survey ◽  
Bayesian Priors ◽  
Energy Survey ◽  
And Task

AbstractBayesian methods are ubiquitous in contemporary observational cosmology. They enter into three main tasks: (I) cross-checking datasets for consistency; (II) fixing constraints on cosmological parameters; and (III) model selection. This article explores some epistemic limits of using Bayesian methods. The first limit concerns the degree of informativeness of the Bayesian priors and an ensuing methodological tension between task (I) and task (II). The second limit concerns the choice of wide flat priors and related tension between (II) parameter estimation and (III) model selection. The Dark Energy Survey (DES) and its recent Year 1 results illustrate both these limits concerning the use of Bayesianism.

scholarly journals First cosmology results using Type IA supernovae from the dark energy survey: effects of chromatic corrections to supernova photometry on measurements of cosmological parameters

2019 ◽  
Vol 485 (4) ◽  
pp. 5329-5344 ◽  
Author(s):  
J Lasker ◽  
R Kessler ◽  
D Scolnic ◽  
D Brout ◽  
D L Burke ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Critical Density ◽  
Transmission Function ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Dark Energy Survey ◽  
Type Ia ◽  
Ia Supernovae ◽  
Energy Survey

Abstract Calibration uncertainties have been the leading systematic uncertainty in recent analyses using Type Ia supernovae (SNe Ia) to measure cosmological parameters. To improve the calibration, we present the application of spectral energy distribution-dependent ‘chromatic corrections’ to the SN light-curve photometry from the Dark Energy Survey (DES). These corrections depend on the combined atmospheric and instrumental transmission function for each exposure, and they affect photometry at the 0.01 mag (1 per cent) level, comparable to systematic uncertainties in calibration and photometry. Fitting our combined DES and low-z SN Ia sample with baryon acoustic oscillation (BAO) and cosmic microwave background (CMB) priors for the cosmological parameters Ωm (the fraction of the critical density of the universe comprised of matter) and w (the dark energy equation of state parameter), we compare those parameters before and after applying the corrections. We find the change in w and Ωm due to not including chromatic corrections is −0.002 and 0.000, respectively, for the DES-SN3YR sample with BAO and CMB priors, consistent with a larger DES-SN3YR-like simulation, which has a w-change of 0.0005 with an uncertainty of 0.008 and an Ωm change of 0.000 with an uncertainty of 0.002. However, when considering samples on individual CCDs we find large redshift-dependent biases (∼0.02 in distance modulus) for SN distances.

scholarly journals Dark Energy Survey Year 1 results: validation of weak lensing cluster member contamination estimates from P(z) decomposition

2019 ◽  
Vol 489 (2) ◽  
pp. 2511-2524 ◽  
Author(s):  
T N Varga ◽  
J DeRose ◽  
D Gruen ◽  
T McClintock ◽  
S Seitz ◽  
...  
Keyword(s):  
Dark Energy ◽  
Decomposition Method ◽  
Weak Lensing ◽  
Cluster Member ◽  
Photometric Redshift ◽  
Cluster Mass ◽  
Dark Energy Survey ◽  
Mass Calibration ◽  
The Masses ◽  
Energy Survey

ABSTRACT Weak lensing source galaxy catalogues used in estimating the masses of galaxy clusters can be heavily contaminated by cluster members, prohibiting accurate mass calibration. In this study, we test the performance of an estimator for the extent of cluster member contamination based on decomposing the photometric redshift P(z) of source galaxies into contaminating and background components. We perform a full scale mock analysis on a simulated sky survey approximately mirroring the observational properties of the Dark Energy Survey Year One observations (DES Y1), and find excellent agreement between the true number profile of contaminating cluster member galaxies in the simulation and the estimated one. We further apply the method to estimate the cluster member contamination for the DES Y1 redMaPPer cluster mass calibration analysis, and compare the results to an alternative approach based on the angular correlation of weak lensing source galaxies. We find indications that the correlation based estimates are biased by the selection of the weak lensing sources in the cluster vicinity, which does not strongly impact the P(z) decomposition method. Collectively, these benchmarks demonstrate the strength of the P(z) decomposition method in alleviating membership contamination and enabling highly accurate cluster weak lensing studies without broad exclusion of source galaxies, thereby improving the total constraining power of cluster mass calibration via weak lensing.

Sign in / Sign up

Export Citation Format

Share Document