Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-05-04
Astronomy and Astrophysics, Volume 507, Issue 1, 2009, pp.105-129
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
26 pages, including 16 figures; minor changes to match accepted version; published in Astronomy and Astrophysics
Scientific paper
10.1051/0004-6361/200912420
Cosmic shear is regarded one of the most powerful probes to reveal the properties of dark matter and dark energy. To fully utilize its potential, one has to be able to control systematic effects down to below the level of the statistical parameter errors. Particularly worrisome in this respect is intrinsic alignment, causing considerable parameter biases via correlations between the intrinsic ellipticities of galaxies and the gravitational shear, which mimic lensing. In an earlier work we have proposed a nulling technique that downweights this systematic, only making use of its well-known redshift dependence. We assess the practicability of nulling, given realistic conditions on photometric redshift information. For several simplified intrinsic alignment models and a wide range of photometric redshift characteristics we calculate an average bias before and after nulling. Modifications of the technique are introduced to optimize the bias removal and minimize the information loss by nulling. We demonstrate that one of the presented versions is close to optimal in terms of bias removal, given high quality of photometric redshifts. For excellent photometric redshift information, i.e. at least 10 bins with a small dispersion, a negligible fraction of catastrophic outliers, and precise knowledge about the redshift distributions, one version of nulling is capable of reducing the shear-intrinsic ellipticity contamination by at least a factor of 100. Alternatively, we describe a robust nulling variant which suppresses the systematic signal by about 10 for a very broad range of photometric redshift configurations. Irrespective of the photometric redshift quality, a loss of statistical power is inherent to nulling, which amounts to a decrease of the order 50% in terms of our figure of merit.
Joachimi Benjamin
Schneider Pat
No associations
LandOfFree
The removal of shear-ellipticity correlations from the cosmic shear signal: Influence of photometric redshift errors on the nulling technique does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The removal of shear-ellipticity correlations from the cosmic shear signal: Influence of photometric redshift errors on the nulling technique, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The removal of shear-ellipticity correlations from the cosmic shear signal: Influence of photometric redshift errors on the nulling technique will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-199632