Mathematics – Logic
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21537601s&link_type=abstract
American Astronomical Society, AAS Meeting #215, #376.01; Bulletin of the American Astronomical Society, Vol. 42, p.584
Mathematics
Logic
Scientific paper
Correlations between intrinsic ellipticities of galaxies are a potentially important systematic error when constraining dark energy properties from weak gravitational lensing (cosmic shear) surveys. We present a new model for the intrinsic alignments of galaxy ellipticities based on the placement of galaxies into dark matter halos. The ellipticity of the central galaxy in a halo follows the large scale potential and, in the simplest case, the satellite galaxies point toward the halo center. Ellipticity correlations between galaxies in different halos are dominated by the linear alignment model and the ellipticity correlations within a single halo provide a motivated extension of intrinsic alignment models to small scales. We illustrate the potential impact of ignoring intrinsic alignments on cosmological parameter constraints from non-tomographic surveys, finding that sigma8 could be underestimated by up to the size of the current 1-sigma error bar from cosmic shear if very small scales are included in the analysis. We also show that including galaxy-shear correlations at low redshift (where the intrinsic alignments dominate) is a promising way to measure properties of the intrinsic alignments in addition to cosmology. Finally, we highlight areas of interest for numerical simulations of dark matter clustering and galaxy formation that can further constrain the intrinsic alignment signal.
Bridle Sarah
Kirk Donnacha
Schneider Michael
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