4 research outputs found
KiDS-1000: Constraints on the intrinsic alignment of luminous red galaxies
We constrain the luminosity and redshift dependence of the intrinsic alignment (IA) of a nearly volume-limited sample of luminous red galaxies selected from the fourth public data release of the Kilo-Degree Survey (KiDS-1000). To measure the shapes of the galaxies, we used two complementary algorithms, finding consistent IA measurements for the overlapping galaxy sample. The global significance of IA detection across our two independent luminous red galaxy samples, with our favoured method of shape estimation, is âŒ10.7Ï. We find no significant dependence with redshift of the IA signal in the range 0.2â<âzâ<â0.8, nor a dependence with luminosity below LrââČâ2.9â
Ăâ
1010âhâ2Lr,ââ. Above this luminosity, however, we find that the IA signal increases as a power law, although our results are also compatible with linear growth within the current uncertainties. This behaviour motivates the use of a broken power law model when accounting for the luminosity dependence of IA contamination in cosmic shear studies
KiDS-1000: Constraints on the intrinsic alignment of luminous red galaxies
Large scale structure and cosmolog
KiDS-1000 Methodology:Modelling and inference for joint weak gravitational lensing and spectroscopic galaxy clustering analysis
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 goodness-of-fit statistic
have been validated, with proposed changes to the number of degrees of freedom.
Standard weak lensing point estimates on 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 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,
constraints are expected to improve by 20% for weak lensing alone and by 29%
for the joint analysis. [abridged]Comment: 45 pages, 34 figures, 7 tables; minor changes to match version
accepted by A&A. The KiDS-1000 data products are available for download at
http://kids.strw.leidenuniv.nl/DR4/lensing.php. This data release includes
open source software, the shear-photo-z catalogue, the cosmic shear and 3x2pt
data vectors and covariances, and posteriors in the form of Multinest chain
Euclid. I. Overview of the Euclid mission
International audienceThe current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance