Using lensing and correlation measurements to correct Finger-of-God
Chiaki Hikage (Nagoya) - February 11, 2013 at 12:10 pm
For decades, cosmologists have been using galaxies to trace the large-scale
distribution of matter. One of the largest systematic uncertainties in this
analysis comes from the non-linear redshift distortion, i.e., Finger-of-God
effect. If all galaxies sat in the centers of halos, there would be minimal
Finger-of-God (FoG) effects and a simple relationship between the galaxy
and matter distributions. However, many galaxies, even some of the luminous
red galaxies (LRGs), do not lie in the centers of halos. Because the
LRG-galaxy lensing and the cross-correlation of LRGs with photometric red
galaxies are also sensitive to the off-centered LRGs, we develop an
approach for using lensing and correlation measurements to determine the
expected amplitude of FoG effects. Using SDSS DR7 LRG and photometric
galaxy datasets, we find that 40 per cent of Brightest LRGs are
off-centered galaxies in the multiple-LRG systems with typical
off-centering radius of ~400 kpc/h, and the velocity dispersion of about
500 km/s inside their host halos. The resulting FoG contamination in the
LRG power spectrum can be significant at k > 0.1 h/Mpc, which may bias
cosmological parameters determined by the shape of the power spectrum, such
as the neutrino mass.
The seminar will be held in B-5 Hearst Field Annex.
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