Intrinsic and extrinsic correlations of galaxy shapes and sizes in weak lensing data

Abstract

The subject of this paper is to build a physical model describing shape and size correlations of galaxies due to weak gravitational lensing and due to direct tidal interaction of elliptical galaxies with gravitational fields sourced by the cosmic large-scale structure. Setting up a linear intrinsic alignment model for elliptical galaxies which parameterises the reaction of the galaxy to an external tidal shear field is controlled by the velocity dispersion, we predict intrinsic correlations and cross-correlations with weak lensing for both shapes and sizes, juxtaposing both types of spectra with lensing. We quantify the observability of the intrinsic shape and size correlations and estimate with the Fisher-formalism how well the alignment parameter can be determined from the Euclid weak lensing survey. Specifically, we find a contamination of the weak lensing convergence spectra with an intrinsic size correlation amounting to up to 10% over a wide multipole range $\ell =100\dots 300$, with a corresponding cross-correlation exhibiting a sign change, similar to the cross-correlation between weak lensing shear and intrinsic shapes. A determination of the alignment parameter yields a precision of a few percent forecasted for Euclid, and we show that all shape and many size correlations should be measurable with Euclid.

16 pages, 6 figures

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Cited by in corpus (9)

• The MillenniumTNG Project: Intrinsic alignments of galaxies and halos
• On the Cosmic Web Elongation in Fuzzy Dark Matter Cosmologies: Effects on Density Profiles, Shapes and Alignments of Halos
• Higher order statistics of shear field: a machine learning approach
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• Intrinsic correlations of galaxy sizes in a hydrodynamical cosmological simulation
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• The Influence of Subhaloes on Host Halo Properties
• Testing modified (Horndeski) gravity by combining intrinsic galaxyalignments with cosmic shear
• Etherington duality breaking: gravitational lensing in non-metric spacetimes versus intrinsic alignments