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Issue A&A
Volume 441, Number 1, October I 2005
Page(s) 47 - 53
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20053330



A&A 441, 47-53 (2005)
DOI: 10.1051/0004-6361:20053330

Cosmic shear as a tool for precision cosmology: minimising intrinsic galaxy alignment-lensing interference

L. J. King

Institute of Astronomy, Cambridge University, Madingley Rd, Cambridge CB3 0HA, UK
    e-mail: ljk@ast.cam.ac.uk

(Received 28 April 2005 / Accepted 14 June 2005 )

Abstract
Cosmic shear leads to a correlation of the observed ellipticities of galaxies, an effect which is used to place constraints on cosmological parameters, and to explore the evolution of dark matter and dark energy in the universe. However, a possible systematic contaminant of the lensing signal is intrinsic galaxy alignment, with a correlation length of a few Mpc. Hirata & Seljak (2004, Phys. Rev. D, 70, 063526) have recently demonstrated that for some models of intrinsic distortions, there may also be a cross-correlation between the intrinsic and lensing signals, which may dominate the intrinsic signal, and suppress the lensing power spectrum by several tens of percent. Unlike the pure intrinsic signal, this new term cannot be accounted for by neglecting or down-weighting pairs of galaxies which are physically close. Extending the correlation function tomography method of King & Schneider (2003, A&A, 398, 23) we illustrate how the impact of both intrinsic and cross-correlations can be significantly reduced, in the context of surveys with photometric redshift information. For a ground-based cosmic shear survey of ~100 sq. degrees with photometric redshifts, even in the presence of systematic contaminants at the level considered here, cosmological models degenerate in the $\Omega_{\rm m}-\sigma_8$ plane can be distinguished well in excess of the 3-$\sigma$ level.


Key words: gravitational lensing -- cosmology: cosmological parameters




© ESO 2005


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