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Do Angular Momentum Induced Ellipticity Correlations Contaminate Weak Lensing Measurements?

Published online by Cambridge University Press:  05 March 2013

Priyamvada Natarajan ,
Robert G. Crittenden ,
Ue-Li Pen  and
Tom Theuns
Priyamvada Natarajan
Affiliation:
Department of Astronomy, Yale University, New Haven, CT, USA; [email protected]
Robert G. Crittenden
Affiliation:
Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA, UK; [email protected]
Ue-Li Pen
Affiliation:
CITA, McLennan Labs, University of Toronto, Toronto, M5S 3H8, Canada; [email protected]
Tom Theuns
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge CB3 0HE, UK; [email protected]
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Abstract

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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 protogalaxies 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 zm = 1, the intrinsic signal is a contaminant on the order of 1–10% of the measured signal. However, for shallower surveys with zm ≤ 0.3, 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.

Keywords

gravitational lensinggalaxies:statistics
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 18 , Issue 2 , 2001 , pp. 198 - 200
Copyright
Copyright © Astronomical Society of Australia 2001

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