Magnification bias in the shearratio test: a viable mitigation strategy
Abstract
Using the same lens galaxies, the ratios of tangential shears for different source galaxy redshifts is equal to the ratios of their corresponding angulardiameter distances. This is the socalled shearratio test (SRT) and it is valid when effects induced by the intervening largescale structure (LSS) can be neglected. The dominant LSS effect is magnification bias which, on the one hand, induces an additional shear, and on the other hand, causes a magnification of the lens population. Our objective is to quantify the magnification bias for the SRT and show an easytoapply mitigation strategy that does not rely on additional observations. We use raytracing data through the Millennium simulation to measure the influence of magnification on the SRT and test our mitigation strategy. Using the SRT as a nulltest we find deviations from zero up to 10% for a fluxlimited sample of lens galaxies, which is a strong function of lens redshift and the lenssource lineofsight separation. Using our mitigation strategy we can improve the nulltest by a factor of ∼100.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 2019
 DOI:
 10.1051/00046361/201834151
 arXiv:
 arXiv:1808.09516
 Bibcode:
 2019A&A...623A..94U
 Keywords:

 gravitational lensing: weak;
 methods: statistical;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 9 pages, 7 figures