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Astronomy Tea Talks at Caltech

Mondays, Robinson 106
Tea:  4.00pm
Talk: 4.15pm

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2007 - 2008 season:
17 March 2008 Tim Eifler (Bonn)

"Cosmological Parameters from Cosmic Shear - Impact of cosmology dependent covariances in a likelihood analysis"


In recent years weak lensing by the large-scale structure of the
Universe, called cosmic shear, has become a valuable probe in cosmology.
Large upcoming surveys like KIDS and Pan-STARRS will improve the quality
of cosmic shear data significantly, enabling us to measure its signal with
less than 1% statistical error. In order to obtain cosmological parameters
from these high precision data properly, there remain issues to address.
On the observational side, the systematic errors, mainly from insufficient
PSF-correction, must be reduced and a possible contribution to the shear
signal coming from intrinsic alignment must be excluded. On the
theoretical side, we need accurate predictions for P_delta(k) and a
precise method for the inference on cosmological parameters.
In this talk I will briefly review the basics of cosmic shear, especially
how to constrain cosmological parameters. I will focus on the impact of
cosmic shear covariances on the parameter estimation, addressing the
assumption of a covariance which is constant in parameter space, how this
influences the likelihood contours and how to improve on this. Finally, I
will quantify the difference between Gaussian and non-Gaussian covariances
and the importance of the ellipticity shape noise for the latter case.
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Last modified on 12th Mar 2008 by Johan Richard.  

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