Fabian Köhlinger

Constraints on the alignment of galaxies in galaxy clusters from ~14 000 spectroscopic members

Torques acting on galaxies lead to physical alignments, but the resulting ellipticity correlations are difficult to predict. As they constitute a major contaminant for cosmic shear studies, it is important to constrain the intrinsic alignment signal observationally. We measured the alignments of satellite galaxies within 90 massive galaxy clusters in the redshift range 0.05<z<0.55 and quantified their impact on the cosmic shear signal. We combined a sample of 38,104 galaxies with spectroscopic redshifts with high-quality data from the Canada-France-Hawaii Telescope. We used phase-space information to select 14,576 cluster members, 14,250 of which have shape measurements and measured three different types of alignment: the radial alignment of satellite galaxies toward the brightest cluster galaxies (BCGs), the common orientations of satellite galaxies and BCGs, and the radial alignments of satellites with each other. Residual systematic effects are much smaller than the statistical uncertainties. We detect no galaxy alignment of any kind out to at least 3 r200. The signal is consistent with zero for both blue and red galaxies, bright and faint ones, and also for subsamples of clusters based on redshift, dynamical mass, and dynamical state. These conclusions are unchanged if we expand the sample with bright cluster members from the red sequence. We augment our constraints with those from the literature to estimate the importance of the intrinsic alignments of satellites compared to those of central galaxies, for which the alignments are described by the linear alignment model. Comparison of the alignment signals to the expected uncertainties of current surveys such as the Kilo-Degree Survey suggests that the linear alignment model is an adequate treatment of intrinsic alignments, but it is not clear whether this will be the case for larger surveys.

KiDS-450 : the tomographic weak lensing power spectrum and constraints on cosmological parameters

We present measurements of the weak gravitational lensing shear power spectrum based on

KiDS+GAMA : Cosmology constraints from a joint analysis of cosmic shear, galaxy-galaxy lensing and angular clustering

450

A direct measurement of tomographic lensing power spectra from CFHTLenS

sq. deg. of imaging data from the Kilo Degree Survey. We employ a quadratic estimator in two and three redshift bins and extract band powers of redshift auto-correlation and cross-correlation spectra in the multipole range

Precision calculations of the cosmic shear power spectrum projection

76 \leq \ell \leq 1310

Statistical uncertainties and systematic errors in weak lensing mass estimates of galaxy clusters

. The cosmological interpretation of the measured shear power spectra is performed in a Bayesian framework assuming a

KiDS-450: Cosmological parameter constraints from tomographic weak gravitational lensing

\Lambda

KiDS-450 : testing extensions to the standard cosmological model

CDM model with spatially flat geometry, while accounting for small residual uncertainties in the shear calibration and redshift distributions as well as marginalising over intrinsic alignments, baryon feedback and an excess-noise power model. Moreover, massive neutrinos are included in the modelling. The cosmological main result is expressed in terms of the parameter combination

A Bayesian quantification of consistency in correlated datasets.

S_8 \equiv \sigma_8 \sqrt{\Omega_{\rm m}/0.3}

Cosmology from cosmic shear power spectra with Subaru Hyper Suprime-Cam first-year data

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