The Sourcelens Clustering Effect in the Context of Lensing Tomography and Its Selfcalibration
Abstract
Cosmic shear can only be measured where there are galaxies. This sourcelens clustering (SLC) effect has two sources, intrinsic source clustering and cosmic magnification (magnification/size bias). Lensing tomography can suppress the former. However, this reduction is limited by the existence of photoz error and nonzero redshift bin width. Furthermore, SLC induced by cosmic magnification cannot be reduced by lensing tomography. Through Nbody simulations, we quantify the impact of SLC on the lensing power spectrum in the context of lensing tomography. We consider both the standard estimator and the pixelbased estimator. We find that none of them can satisfactorily handle both sources of SLC. (1) For the standard estimator, SLC induced by both sources can bias the lensing power spectrum by O≤ft( 1 \right)O(10)%. Intrinsic source clustering also increases statistical uncertainties in the measured lensing power spectrum. However, the standard estimator suppresses intrinsic source clustering in the crossspectrum. (2) In contrast, the pixelbased estimator suppresses SLC through cosmic magnification. However, it fails to suppress SLC through intrinsic source clustering and the measured lensing power spectrum can be biased low by O≤ft( 1 \right)O(10)%. In short, for typical photoz errors ({σ }_{z}}/≤ft( 1+z \right)=0.05) and photoz bin sizes ({Δ{{z}^{P}}=0.2), SLC alters the lensing Emode power spectrum by 110%, with \ell ∼ {{10}^{3}} and {{z}_{s}}∼ 1 being of particular interest to weak lensing cosmology. Therefore the SLC is a severe systematic for cosmology in StageIV lensing surveys. We present useful scaling relations to selfcalibrate the SLC effect.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 2015
 DOI:
 10.1088/0004637X/803/1/46
 arXiv:
 arXiv:1402.7144
 Bibcode:
 2015ApJ...803...46Y
 Keywords:

 gravitational lensing: weak;
 largescale structure of universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 13 pages, 10 figures, Accepted by APJ