Issue |
A&A
Volume 417, Number 3, April III 2004
|
|
---|---|---|
Page(s) | 873 - 885 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20034251 | |
Published online | 26 March 2004 |
The covariance of cosmic shear correlation functions and cosmological parameter estimates using redshift information
Institut für Astrophysik und Extraterrestrische Forschung, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
Corresponding author: P. Simon, psimon@astro.uni-bonn.de
Received:
1
September
2003
Accepted:
13
January
2004
Cosmological
weak lensing by the large scale structure of the Universe, cosmic
shear, is coming of age as a powerful probe of the parameters
describing the cosmological model and matter power spectrum. It
complements Cosmic Microwave Background studies, by breaking
degeneracies and providing a cross-check. Furthermore, upcoming
cosmic shear surveys with photometric redshift information will
enable the evolution of dark matter to be studied, and even a crude
separation of sources into redshift bins leads to improved
constraints on parameters. An important measure of the cosmic shear
signal are the shear correlation functions; these can be directly
calculated from data, and compared with theoretical expectations for
different cosmological models and matter power spectra. We present a
Monte Carlo method to quickly simulate mock cosmic shear surveys.
One application of this method is in the determination of the full
covariance matrix for the correlation functions; this includes
redshift binning and is applicable to arbitrary survey geometries.
Terms arising from shot noise and cosmic variance (dominant on small
and large scales respectively) are accounted for naturally. As an
illustration of the use of such covariance matrices, we consider to
what degree confidence regions on parameters are tightened when
redshift binning is employed. The parameters considered are those
commonly discussed in cosmic shear analyses – the matter density
parameter , dark energy density parameter (classical
cosmological constant)
, power spectrum
normalisation
and shape parameter Γ. We
incorporate our covariance matrices into a likelihood treatment, and
also use the Fisher formalism to explore a larger region of
parameter space. Parameter uncertainties can be decreased by a
factor of ∼4-8 (∼5-10) with 2 (4) redshift bins.
Key words: cosmology: large-scale structure of Universe / cosmology: theory / gravitational lensing / methods: numerical
© ESO, 2004
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