Systematic effects on dark energy from 3D weak shear
Systematic effects on dark energy from 3D weak shear
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DOI：
10.1111/j.1365-2966.2008.13419.x
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发表时间：
2008-01
影响因子：
4.8
通讯作者：
T. Kitching;A. Taylor;A. Heavens
中科院分区：
文献类型：
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作者：
T. Kitching;A. Taylor;A. Heavens
我们研究了多波段宽视场测量中固有的系统学对两种 3D 弱透镜方法的暗能量状态方程确定的潜在影响。弱透镜方法是几何剪切比法和3D 宇宙剪切法。这里的分析使用费希尔矩阵框架的扩展，包括联合光度红移系统学、剪切畸变系统学和内在对准。使用这三个主要系统效应的分析参数化可以隔离特别重要的系统参数。我们表明，假设系统参数是固定的，但可能有偏差，会导致暗能量参数存在潜在的巨大偏差。我们通过定义偏差品质因数来量化任何潜在偏差。通过边缘化额外的系统参数，这种偏差被消除，但代价是宇宙学参数误差的增加。我们分别展示了每个系统参数边缘化对暗能量品质因数的影响。我们还显示了由于所有三种类型的系统效应而导致的品质因数的总体下降。基于对系统误差可能水平的一些假设，我们发现对品质因数的最大影响来自光度红移系统参数的不确定性。如果没有应用有关系统参数的信息，这些可以将两种 3D 弱透镜方法中的品质因数降低多达 2 至 4 倍。剪切畸变系统的总体影响较小。内在的对齐效应可以将品质因数进一步降低 2 倍。然而，在所使用的参数化假设范围内，这是最坏的情况。通过包含系统参数的先验信息，可以在很大程度上恢复品质因数，并且 3D 宇宙剪切和剪切比的组合约束对于系统学来说是稳健的。我们的结论是，根据经验，考虑到当前对内在对准和光度红移的现实理解，然后将所有三个主要系统效应纳入其中，品质因数最多会降低 2 倍。
We present an investigation into the potential effect of systematics inherent in multiband wide-field surveys on the dark energy equation-of-state determination for two 3D weak lensing methods. The weak lensing methods are a geometric shear-ratio method and 3D cosmic shear. The analysis here uses an extension of the Fisher matrix framework to include jointly photometric redshift systematics, shear distortion systematics and intrinsic alignments. Using analytic parametrizations of these three primary systematic effects allows an isolation of systematic parameters of particular importance. We show that assuming systematic parameters are fixed, but possibly biased, results in potentially large biases in dark energy parameters. We quantify any potential bias by defining a Bias Figure of Merit. By marginalizing over extra systematic parameters, such biases are negated at the expense of an increase in the cosmological parameter errors. We show the effect on the dark energy Figure of Merit of marginalizing over each systematic parameter individually. We also show the overall reduction in the Figure of Merit due to all three types of systematic effects. Based on some assumption of the likely level of systematic errors, we find that the largest effect on the Figure of Merit comes from uncertainty in the photometric redshift systematic parameters. These can reduce the Figure of Merit by up to a factor of 2 to 4 in both 3D weak lensing methods, if no informative prior on the systematic parameters is applied. Shear distortion systematics have a smaller overall effect. Intrinsic alignment effects can reduce the Figure of Merit by up to a further factor of 2. This, however, is a worst-case scenario, within the assumptions of the parametrizations used. By including prior information on systematic parameters, the Figure of Merit can be recovered to a large extent, and combined constraints from 3D cosmic shear and shear ratio are robust to systematics. We conclude that, as a rule of thumb, given a realistic current understanding of intrinsic alignments and photometric redshifts, then including all three primary systematic effects reduces the Figure of Merit by at most a factor of 2.