We present a combined tomographic weak gravitational lensing analysis of the Kilo Degree Survey (KV450) and the Dark Energy Survey (DES-Y1). We homogenize the analysis of these two public cosmic ...shear datasets by adopting consistent priors and modeling of nonlinear scales, and determine new redshift distributions for DES-Y1 based on deep public spectroscopic surveys. Adopting these revised redshifts results in a \(0.8\sigma\) reduction in the DES-inferred value for \(S_8\), which decreases to a \(0.5\sigma\) reduction when including a systematic redshift calibration error model from mock DES data based on the MICE2 simulation. The combined KV450 + DES-Y1 constraint on \(S_8 = 0.762^{+0.025}_{-0.024}\) is in tension with the Planck 2018 constraint from the cosmic microwave background at the level of \(2.5\sigma\). This result highlights the importance of developing methods to provide accurate redshift calibration for current and future weak lensing surveys.
We evaluate the consistency between lensing and clustering probes of
large-scale structure based on measurements of projected galaxy clustering from
BOSS combined with overlapping galaxy-galaxy ...lensing from three surveys: DES
Y3, HSC Y1, and KiDS-1000. An intra-lensing-survey study finds good agreement
between these lensing data. We model the observations using the Dark Emulator
and fit the data at two fixed cosmologies: Planck, with $S_8=0.83$, and a
Lensing cosmology with $S_8=0.76$. For a joint analysis limited to scales with
$R>5.25h^{-1}$Mpc, we find that both cosmologies provide an acceptable fit to
the data. Full utilisation of the small-scale clustering and lensing
measurements is hindered by uncertainty in the impact of baryon feedback and
assembly bias, which we account for with a reasoned theoretical error budget.
We incorporate a systematic scaling parameter for each redshift bin, $A$, that
decouples the lensing and clustering to capture any inconsistency. When a wide
range of scales ($0.15<R<60h^{-1}$Mpc) are incorporated, we find different
results for the consistency of clustering and lensing between the two
cosmologies. Limiting the analysis to the bins for which the impact of the
selection of the lens sample is expected to be minimal, for the low-$S_8$
Lensing cosmology, the measurements are consistent with $A$=1; $A=0.91\pm0.04$
using DES+KiDS and $A=0.97\pm0.06$ using HSC. For the Planck cosmology case, we
find a discrepancy: $A=0.79\pm0.03$ using DES+KiDS and $A=0.84\pm0.05$ using
HSC. We demonstrate that a kSZ-based estimate for baryonic effects alleviates
some of the discrepancy in the Planck cosmology. This analysis demonstrates the
statistical power of these small-scale measurements, but also indicates that
caution is still warranted given current uncertainties in modelling baryonic
effects, assembly bias, and selection effects in the foreground sample.
We present the methodology for a joint cosmological analysis of weak gravitational lensing from the fourth data release of the ESO Kilo-Degree Survey (KiDS-1000) and galaxy clustering from the ...partially overlapping BOSS and 2dFLenS surveys. Cross-correlations between galaxy positions and ellipticities have been incorporated into the analysis, necessitating a hybrid model of non-linear scales that blends perturbative and non-perturbative approaches, and an assessment of contributions by astrophysical effects. All weak lensing signals are measured consistently via Fourier-space statistics that are insensitive to the survey mask and display low levels of mode mixing. The calibration of photometric redshift distributions and multiplicative gravitational shear bias has been updated, and a more complete tally of residual calibration uncertainties is propagated into the likelihood. A dedicated suite of more than 20000 mocks is used to assess the performance of covariance models and to quantify the impact of survey geometry and spatial variations of survey depth on signals and their errors. The sampling distributions for the likelihood and the \(\chi^2\) goodness-of-fit statistic have been validated, with proposed changes to the number of degrees of freedom. Standard weak lensing point estimates on \(S_8=\sigma_8\,(\Omega_{\rm m}/0.3)^{1/2}\) derived from its marginal posterior are easily misinterpreted to be biased low, and an alternative estimator and associated credible interval have been proposed. Known systematic effects pertaining to weak lensing modelling and inference are shown to bias \(S_8\) by no more than 0.1 standard deviations, with the caveat that no conclusive validation data exist for models of intrinsic galaxy alignments. Compared to the previous KiDS analyses, \(S_8\) constraints are expected to improve by 20% for weak lensing alone and by 29% for the joint analysis. abridged
Lensing Without Borders is a cross-survey collaboration created to assess the consistency of galaxy-galaxy lensing signals (\(\Delta\Sigma\)) across different data-sets and to carry out end-to-end ...tests of systematic errors. We perform a blind comparison of the amplitude of \(\Delta\Sigma\) using lens samples from BOSS and six independent lensing surveys. We find good agreement between empirically estimated and reported systematic errors which agree to better than 2.3\(\sigma\) in four lens bins and three radial ranges. For lenses with \(z_{\rm L}>0.43\) and considering statistical errors, we detect a 3-4\(\sigma\) correlation between lensing amplitude and survey depth. This correlation could arise from the increasing impact at higher redshift of unrecognised galaxy blends on shear calibration and imperfections in photometric redshift calibration. At \(z_{\rm L}>0.54\) amplitudes may additionally correlate with foreground stellar density. The amplitude of these trends is within survey-defined systematic error budgets which are designed to include known shear and redshift calibration uncertainty. Using a fully empirical and conservative method, we do not find evidence for large unknown systematics. Systematic errors greater than 15% (25%) ruled out in three lens bins at 68% (95%) confidence at \(z<0.54\). Differences with respect to predictions based on clustering are observed to be at the 20-30% level. Our results therefore suggest that lensing systematics alone are unlikely to fully explain the "lensing is low" effect at \(z<0.54\). This analysis demonstrates the power of cross-survey comparisons and provides a promising path for identifying and reducing systematics in future lensing analyses.
We present a public suite of weak lensing mock data, extending the Scinet Light Cone Simulations (SLICS) to simulate cross-correlation analyses with different cosmological probes. These mocks include ...KiDS-450- and LSST-like lensing data, cosmic microwave background lensing maps and simulated spectroscopic surveys that emulate the GAMA, BOSS and 2dFLenS galaxy surveys. With 844 independent realisations, our mocks are optimised for combined-probe covariance estimation, which we illustrate for the case of a joint measurement involving cosmic shear, galaxy-galaxy lensing and galaxy clustering from KiDS-450 and BOSS data. With their high spatial resolution, the SLICS are also optimal for predicting the signal for novel lensing estimators, for the validation of analysis pipelines, and for testing a range of systematic effects such as the impact of neighbour-exclusion bias on the measured tomographic cosmic shear signal. For surveys like KiDS and DES, where the rejection of neighbouring galaxies occurs within ~2 arcseconds, we show that the measured cosmic shear signal will be biased low, but by less than a percent on the angular scales that are typically used in cosmic shear analyses. The amplitude of the neighbour-exclusion bias doubles in deeper, LSST-like data. The simulation products described in this paper are made available at http://slics.roe.ac.uk/.
We present a tomographic cosmic shear analysis of the Kilo-Degree Survey (KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey (VIKING). This is the first time that a full optical to ...near-infrared data set has been used for a wide-field cosmological weak lensing experiment. This unprecedented data, spanning \(450~\)deg\(^2\), allows us to improve significantly the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and - most importantly - solidify our knowledge of the redshift distributions of the sources. Based on a flat \(\Lambda\)CDM model we find \(S_8\equiv\sigma_8\sqrt{\Omega_{\rm m}/0.3}=0.737_{-0.036}^{+0.040}\) in a blind analysis from cosmic shear alone. The tension between KiDS cosmic shear and the Planck-Legacy CMB measurements remains in this systematically more robust analysis, with \(S_8\) differing by \(2.3\sigma\). This result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS shear measurements are calibrated with a new, more realistic set of image simulations and no significant B-modes are detected in the survey, indicating that systematic errors are under control. When calibrating our redshift distributions by assuming the 30-band COSMOS-2015 photometric redshifts are correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we find the tension with Planck is alleviated. The robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys.
We present a weak gravitational lensing analysis of 815 square degree of \(i\)-band imaging from the Kilo-Degree Survey (KiDS-\(i\)-800). In contrast to the deep \(r\)-band observations, which take ...priority during excellent seeing conditions and form the primary KiDS dataset (KiDS-\(r\)-450), the complementary yet shallower KiDS-\(i\)-800 spans a wide range of observing conditions. The overlapping KiDS-\(i\)-800 and KiDS-\(r\)-450 imaging therefore provides a unique opportunity to assess the robustness of weak lensing measurements. In our analysis, we introduce two new `null' tests. The `nulled' two-point shear correlation function uses a matched catalogue to show that the calibrated KiDS-\(i\)-800 and KiDS-\(r\)-450 shear measurements agree at the level of \(1 \pm 4\)\%. We use five galaxy lens samples to determine a `nulled' galaxy-galaxy lensing signal from the full KiDS-\(i\)-800 and KiDS-\(r\)-450 surveys and find that the measurements agree to \(7 \pm 5\)\% when the KiDS-\(i\)-800 source redshift distribution is calibrated using either spectroscopic redshifts, or the 30-band photometric redshifts from the COSMOS survey.
Our aim is to quantify the impact of systematic effects on the inference of cosmological parameters from cosmic shear. We present an end-to-end approach that introduces sources of bias in a modelled ...weak lensing survey on a galaxy-by-galaxy level. Residual biases are propagated through a pipeline from galaxy properties (one end) through to cosmic shear power spectra and cosmological parameter estimates (the other end), to quantify how imperfect knowledge of the pipeline changes the maximum likelihood values of dark energy parameters. We quantify the impact of an imperfect correction for charge transfer inefficiency (CTI) and modelling uncertainties of the point spread function (PSF) for Euclid, and find that the biases introduced can be corrected to acceptable levels.
We evaluate the consistency between lensing and clustering probes of large-scale structure based on measurements of projected galaxy clustering from BOSS combined with overlapping galaxy-galaxy ...lensing from three surveys: DES Y3, HSC Y1, and KiDS-1000. An intra-lensing-survey study finds good agreement between these lensing data. We model the observations using the Dark Emulator and fit the data at two fixed cosmologies: Planck, with \(S_8=0.83\), and a Lensing cosmology with \(S_8=0.76\). For a joint analysis limited to scales with \(R>5.25h^{-1}\)Mpc, we find that both cosmologies provide an acceptable fit to the data. Full utilisation of the small-scale clustering and lensing measurements is hindered by uncertainty in the impact of baryon feedback and assembly bias, which we account for with a reasoned theoretical error budget. We incorporate a systematic scaling parameter for each redshift bin, \(A\), that decouples the lensing and clustering to capture any inconsistency. When a wide range of scales (\(0.15<R<60h^{-1}\)Mpc) are incorporated, we find different results for the consistency of clustering and lensing between the two cosmologies. Limiting the analysis to the bins for which the impact of the selection of the lens sample is expected to be minimal, for the low-\(S_8\) Lensing cosmology, the measurements are consistent with \(A\)=1; \(A=0.91\pm0.04\) using DES+KiDS and \(A=0.97\pm0.06\) using HSC. For the Planck cosmology case, we find a discrepancy: \(A=0.79\pm0.03\) using DES+KiDS and \(A=0.84\pm0.05\) using HSC. We demonstrate that a kSZ-based estimate for baryonic effects alleviates some of the discrepancy in the Planck cosmology. This analysis demonstrates the statistical power of these small-scale measurements, but also indicates that caution is still warranted given current uncertainties in modelling baryonic effects, assembly bias, and selection effects in the foreground sample.
We present a joint cosmological analysis of weak gravitational lensing observations from the Kilo-Degree Survey (KiDS-1000), with redshift-space galaxy clustering observations from the Baryon ...Oscillation Spectroscopic Survey (BOSS) and galaxy-galaxy lensing observations from the overlap between KiDS-1000, BOSS, and the spectroscopic 2-degree Field Lensing Survey. This combination of large-scale structure probes breaks the degeneracies between cosmological parameters for individual observables, resulting in a constraint on the structure growth parameter
S
8
= σ
8
√(Ω
m
/0.3) = 0.766
−0.014
+0.020
, which has the same overall precision as that reported by the full-sky cosmic microwave background observations from
Planck
. The recovered
S
8
amplitude is low, however, by 8.3 ± 2.6% relative to
Planck
. This result builds from a series of KiDS-1000 analyses where we validate our methodology with variable depth mock galaxy surveys, our lensing calibration with image simulations and null-tests, and our optical-to-near-infrared redshift calibration with multi-band mock catalogues and a spectroscopic-photometric clustering analysis. The systematic uncertainties identified by these analyses are folded through as nuisance parameters in our cosmological analysis. Inspecting the offset between the marginalised posterior distributions, we find that the
S
8
-difference with
Planck
is driven by a tension in the matter fluctuation amplitude parameter,
σ
8
. We quantify the level of agreement between the cosmic microwave background and our large-scale structure constraints using a series of different metrics, finding differences with a significance ranging between ∼3
σ
, when considering the offset in
S
8
, and ∼2
σ
, when considering the full multi-dimensional parameter space.
PDF