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How the cosmic web induces intrinsic alignments of galaxies

Published online by Cambridge University Press:  12 October 2016

S. Codis*
Affiliation:
Sorbonne Universités, UPMC Univ. Paris 06 & CNRS, UMR7095, Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, 75014, Paris, France
Y. Dubois
Affiliation:
Sorbonne Universités, UPMC Univ. Paris 06 & CNRS, UMR7095, Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, 75014, Paris, France
C. Pichon
Affiliation:
Sorbonne Universités, UPMC Univ. Paris 06 & CNRS, UMR7095, Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, 75014, Paris, France
J. Devriendt
Affiliation:
Sub-department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH
A. Slyz
Affiliation:
Sub-department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH
*
Email: codis@iap.fr
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Abstract

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Intrinsic alignments are believed to be a major source of systematics for future generation of weak gravitational lensing surveys like Euclid or LSST. Direct measurements of the alignment of the projected light distribution of galaxies in wide field imaging data seem to agree on a contamination at a level of a few per cent of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use dark matter-only simulations as the sole resource to predict and control intrinsic alignments. We report here estimates on the level of intrinsic alignment in the cosmological hydrodynamical simulation Horizon-AGN that could be a major source of systematic errors in weak gravitational lensing measurements. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, we show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded. We will also present theoretical calculations that illustrate and qualitatively explain the observed signals.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2016 

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