Magnification bias in the shear-ratio test: a viable mitigation strategy
Magnification bias in the shear-ratio test: a viable mitigation strategy
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DOI：
10.1051/0004-6361/201834151
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发表时间：
2018-08
影响因子：
6.5
通讯作者：
S. Unruh;P. Schneider;S. Hilbert
中科院分区：
文献类型：
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作者：
S. Unruh;P. Schneider;S. Hilbert
使用相同的透镜星系，不同源星系红移的切向切变的比率等于它们相应的角径距离的比率。这就是所谓的剪力比试验(SRT)，当可以忽略中间大尺度结构(LSS)的影响时，它是有效的。主要的LSS效应是放大偏差，它一方面会引起额外的剪切，另一方面会导致透镜数量的放大。我们的目标是量化SRT的放大偏差，并展示一种易于应用的缓解策略，它不依赖于额外的观测。我们使用千禧年模拟的光线跟踪数据来测量放大倍率对SRT的影响，并测试我们的缓解策略。使用SRT作为零检验，我们发现对于通量有限的透镜星系样本，偏差从零到10%，这是透镜红移和透镜-源视线分离的强烈函数。使用我们的缓解策略，我们可以将空测试提高到∼的100倍。
Using the same lens galaxies, the ratios of tangential shears for different source galaxy redshifts is equal to the ratios of their corresponding angular-diameter distances. This is the so-called shear-ratio test (SRT) and it is valid when effects induced by the intervening large-scale 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 easy-to-apply mitigation strategy that does not rely on additional observations. We use ray-tracing data through the Millennium simulation to measure the influence of magnification on the SRT and test our mitigation strategy. Using the SRT as a null-test we find deviations from zero up to 10% for a flux-limited sample of lens galaxies, which is a strong function of lens redshift and the lens-source line-of-sight separation. Using our mitigation strategy we can improve the null-test by a factor of ∼100.