Johnston, H;
Georgiou, C;
Joachimi, B;
Hoekstra, H;
Chisari, NE;
Farrow, D;
Fortuna, MC;
... Wright, A; + view all
(2019)
KiDS+GAMA: Intrinsic alignment model constraints for current and future weak lensing cosmology.
Astronomy & Astrophysics
, 624
, Article A30. 10.1051/0004-6361/201834714.
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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 (∼9σ) 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 S₈ and the dark energy equation of state w₀, 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.
| Type: | Article |
|---|---|
| Title: | KiDS+GAMA: Intrinsic alignment model constraints for current and future weak lensing cosmology |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1051/0004-6361/201834714 |
| Publisher version: | https://doi.org/10.1051/0004-6361/201834714 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | gravitational lensing: weak, cosmology: observations, large-scale structure of Universe |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10071885 |
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