Other
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...209.7727m&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #77.27; Bulletin of the American Astronomical Society, V
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1
Scientific paper
Cosmic shear, or weak lensing by large-scale structure, has been used to constrain the matter power spectrum normalization around z ˜ 1, and future surveys are being planned to allow high signal-to-noise measurements of cosmic shear to constrain the equation of state of dark energy. One potential systematic error is the correlation between the intrinsic ellipticities of galaxies and the density field that causes gravitational lensing (GI correlation). We describe the original detection of GI correlations to 60/h Mpc scales using galaxies from the Main spectroscopic sample of the Sloan Digital Sky Survey (SDSS) around z ˜ 0.1, followed by a measurement of the scaling with luminosity and redshift for the red galaxies in the SDSS Luminous Red Galaxy sample around z ˜ 0.25. This highly statistically significant detection of GI correlations for galaxies brighter than L* has a sign predicted by theoretical models. The GI correlation could cause the existing lensing surveys at z ˜ 1 to underestimate the linear amplitude of fluctuations by as much as 20% depending on the source sample used. The GI contamination is dominated by the brightest galaxies, possibly due to anisotropic infall along filaments, although other sources of contamination cannot be excluded at this point. Unlike autocorrelations between galaxy intrinsic ellipticities (II correlations), the GI correlations cannot be eliminated by cross-correlating galaxy samples at different redshifts, and in fact are enhanced by this procedure. We discuss methods for eliminating GI contamination in current and future weak lensing surveys, particularly those with data in multiple passbands that allow for the exclusion of the brightest red galaxies, and show what fraction of a typical survey would need to be excluded to reduce the contamination to the sub-percent levels needed for precision cosmology.
Hirata Christopher M.
Ishak Mustapha
Mandelbaum Rachel
Seljak Uros
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