Ambiguities in gravitational lens models: impact on time delays of the source position transformation
Ambiguities in gravitational lens models: impact on time delays of the source position transformation
复制标题
引力透镜模型中的模糊性：对源位置变换的时间延迟的影响
DOI：
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发表时间：
2017
影响因子：
6.5
通讯作者：
P. Schneider
中科院分区：
文献类型：
--
作者：
O. Wertz;Bastian Orthen;P. Schneider
现代延时宇宙学的核心目标在于以具有竞争力的精度确定哈勃常数 H0。然而，从普朗克卫星获得的空间平坦ΛCDM宇宙学中的H0张力表明系统误差可能被低估了。这些错误中最关键的可能来自于透镜模型之间存在的简并性，这种简并性首先由众所周知的质量片变换 (MST) 形式化。在本文中，我们评估了源位置变换（SPT）（一种更通用的不变性变换，其中包含 MST 作为特例）可能在多大程度上影响模型预测的时间延迟。为此，我们使用了 pySPT，这是一个新的开源 Python 包，完全专用于我们在配套论文中介绍的 SPT。对于轴对称透镜，我们发现模型与其 SPT 修改后的对应模型之间的时间延迟比简单地像相应的源位置比一样缩放，Δtˆ/Δt ≈ βˆ/β，而不管质量分布和各向同性 SPT。类似的行为（几乎）适用于双图像区域中的非轴对称透镜和四重图像区域中的相反图像对。在后一种情况下，我们还确认时间延迟比不守恒。除了 MST 效应之外，对于特定图像对，SPT 修改的时间延迟偏差通常不超过几个百分点，这表明它对时间延迟宇宙学的影响似乎并不像最初怀疑的那么重要。我们还反思了 SPT 有效性标准的相关性，并提出了建议重新考虑该标准的论点。尽管新的有效性标准会以不同的方式影响时间延迟，但我们从数值模拟中预计我们的结论将保持不变。
The central ambition of the modern time delay cosmography consists in determining the Hubble constant H0 with a competitive precision. However, the tension with H0 obtained from the Planck satellite for a spatially flat ΛCDM cosmology suggests that systematic errors may have been underestimated. The most critical of these errors probably comes from the degeneracy existing between lens models that was first formalized by the well-known mass-sheet transformation (MST). In this paper, we assess to what extent the source position transformation (SPT), a more general invariance transformation which contains the MST as a special case, may affect the time delays predicted by a model. To this aim, we have used pySPT, a new open-source python package fully dedicated to the SPT that we present in a companion paper. For axisymmetric lenses, we find that the time delay ratios between a model and its SPT-modified counterpart simply scale like the corresponding source position ratios, Δtˆ/Δt ≈ βˆ/β, regardless of the mass profile and the isotropic SPT. Similar behavior (almost) holds for nonaxisymmetric lenses in the double image regime and for opposite image pairs in the quadruple image regime. In the latter regime, we also confirm that the time delay ratios are not conserved. In addition to the MST effects, the SPT-modified time delays deviate in general no more than a few percent for particular image pairs, suggesting that its impact on time delay cosmography seems not be as crucial as initially suspected. We also reflected upon the relevance of the SPT validity criterion and present arguments suggesting that it should be reconsidered. Even though a new validity criterion would affect the time delays in a different way, we expect from numerical simulations that our conclusions will remain unchanged.
质量片简并性、幂律模型和外部会聚：对通过引力透镜确定哈勃常数的影响
影响因子：
6.5
作者：
P. Schneider;D. Sluse
通讯作者：
D. Sluse
源位置变换：强引力透镜中的近似不变性
影响因子：
6.5
作者：
P. Schneider;D. Sluse
通讯作者：
D. Sluse
影响因子：
4.8
作者：
Bonvin, V.;Courbin, F.;Spiniello, C.
通讯作者：
Spiniello, C.