Article

KiDS+GAMA: Intrinsic alignment model constraints for current and future weak lensing cosmology

Harry JohnstonDepartment of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UKChristos GeorgiouLeiden Observatory, Leiden University, PO Box 9513, Leiden 2300 RA, The NetherlandsB. JoachimiDepartment of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UKHenk HoekstraLeiden Observatory, Leiden University, PO Box 9513, Leiden 2300 RA, The NetherlandsNora Elisa ChisariDepartment of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UKDaniel J. FarrowMax-Planck-Institut für extraterrestrische Physik, Postfach 1312 Giessenbachstrasse, 85741 Garching, GermanyMaria Cristina FortunaLeiden Observatory, Leiden University, PO Box 9513, Leiden 2300 RA, The NetherlandsCatherine HeymansScottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UKShahab JoudakiDepartment of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UKKonrad KuijkenLeiden Observatory, Leiden University, PO Box 9513, Leiden 2300 RA, The NetherlandsAngus H. WrightArgelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

2019en

ABI

Abstract

We directly constrain the non-linear alignment (NLA) model of intrinsic galaxy alignments, analysing the most representative and complete flux-limited sample of spectroscopic galaxies available for cosmic shear surveys. We measure the projected galaxy position-intrinsic shear correlations and the projected galaxy clustering signal using high-resolution imaging from the Kilo Degree Survey (KiDS) overlapping with the GAMA spectroscopic survey, and data from the Sloan Digital Sky Survey. Separating samples by colour, we make no significant detection of blue galaxy alignments, constraining the blue galaxy NLA amplitude A IA B = 0.21 −0.36 +0.37 to be consistent with zero. We make robust detections (∼9 σ ) for red galaxies, with A IA R = 3.18 −0.46 +0.47 , corresponding to a net radial alignment with the galaxy density field, and we find no evidence for any scaling of alignments with galaxy luminosity. We provide informative priors for current and future weak lensing surveys, an improvement over de facto wide priors that allow for unrealistic levels of intrinsic alignment contamination. For a colour-split cosmic shear analysis of the final KiDS survey area, we forecast that our priors will improve the constraining power on S 8 and the dark energy equation of state w 0 , by up to 62% and 51%, respectively. Our results indicate, however, that the modelling of red/blue-split galaxy alignments may be insufficient to describe samples with variable central/satellite galaxy fractions.

Identifiers

DOI: 10.1051/0004-6361/201834714

Citations and references

Cited by 10 references

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