Do angular momentum induced ellipticity correlations contaminate weak lensing measurements?

Abstract

Alignments in the angular momentum vectors of galaxies can induce large scale correlations in their projected orientations. Such alignments arise from the tidal torques exerted on neighboring proto-galaxies by the smoothly varying shear field. Weak gravitational lensing can also induce ellipticity correlations since the images of neighboring galaxies will be distorted coherently by the intervening mass distribution. Comparing these two sources of shape correlations, it is found that for current weak lensing surveys with a median redshift of 1, the intrinsic signal is a contaminant on the order of 1-10% of the measured signal. However, for shallower surveys, the intrinsic correlations dominate over the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This difference can be used to disentangle these two sources of ellipticity correlations. When the distortions are dominated by lensing, as occurs at high redshifts, the decomposition provides a valuable tool for understanding properties of the noise and systematic errors.

4 pages, LaTeX, 2 figures, OzLens Workshop proceedings

References in corpus (4)

• Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales
• Detection of Weak Gravitational Lensing by Large-scale Structure
• Intrinsic Correlation of Galaxy Shapes: Implications for Weak Lensing Measurements
• Cosmic Shear from Galaxy Spins

Cited by in corpus (9)

• The Angular Momentum of Gas in Proto-Galaxies I. Implications for the Formation of Disk Galaxies
• Origins of weak lensing systematics, and requirements on future instrumentation (or knowledge of instrumentation)
• Angular ellipticity correlations in a composite alignment model for elliptical and spiral galaxies and inference from weak lensing
• Weak gravitational lensing of intrinsically aligned galaxies
• Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy colour information
• Evolution of intrinsic ellipticity correlations due to peculiar motion
• Dynamical Tidal Locking Theory: A new source of the Spin of Dark Matter Halos
• Intrinsic and extrinsic gravitational flexions
• Realistic systematic biases induced by residual intrinsic alignments in cosmic shear surveys