arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1708.09247astro-ph.COastro-ph.GA
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超越线性星系排列

Beyond linear galaxy alignments

Jonathan Blazek, Niall MacCrann, M. A. Troxel, Xiao Fang

摘要:

星系内禀排列(IA)是当前和未来弱透镜测量的关键不确定性。我们描述了微扰膨胀IA,类似于治疗星系偏置。从天体物理学的角度来看,这个模型包括预期的大规模的星系,压力支持(潮汐对齐)和旋转支持(潮汐扭矩)以及两者之间的互相关的对齐机制。或者,这种扩展可以被看作是一个有效的模型,捕获所有相关的影响,直到给定的顺序。我们包括在密度和潮汐领域的第二顺序的条款,并计算由此产生的IA的贡献,两点统计在一个循环的顺序。对于IA参数的基准振幅,我们发现二次对齐和线性二次交叉项可以贡献阶单位校正的总内在对齐信号在$k\sim0.1\,h^{-1}{\rm Mpc}$,这取决于源的红移分布。这些贡献可能会导致显着的偏差推断宇宙学参数在第四阶段光度弱透镜调查。我们进行预测的LSST样的调查,发现使用标准的“NLA”模型的内在对齐不能删除这些大的参数偏差,即使允许更一般的红移依赖。这里提出的模型将允许更准确和灵活的IA治疗弱透镜和组合探头分析,并实现可作为公共FAST-PT代码的一部分。该模型还提供了一个更先进的框架,了解潜在的IA过程及其与基础物理的关系。

英文摘要:

Galaxy intrinsic alignments (IA) are a critical uncertainty for current and future weak lensing measurements. We describe a perturbative expansion of IA, analogous to the treatment of galaxy biasing. From an astrophysical perspective, this model includes the expected large-scale alignment mechanisms for galaxies that are pressure-supported (tidal alignment) and rotation-supported (tidal torquing) as well as the cross-correlation between the two. Alternatively, this expansion can be viewed as an effective model capturing all relevant effects up to the given order. We include terms up to second order in the density and tidal fields and calculate the resulting IA contributions to two-point statistics at one-loop order. For fiducial amplitudes of the IA parameters, we find the quadratic alignment and linear-quadratic cross terms can contribute order-unity corrections to the total intrinsic alignment signal at $k\sim0.1\,h^{-1}{\rm Mpc}$, depending on the source redshift distribution. These contributions can lead to significant biases on inferred cosmological parameters in Stage IV photometric weak lensing surveys. We perform forecasts for an LSST-like survey, finding that use of the standard "NLA" model for intrinsic alignments cannot remove these large parameter biases, even when allowing for a more general redshift dependence. The model presented here will allow for more accurate and flexible IA treatment in weak lensing and combined probes analyses, and an implementation is made available as part of the public FAST-PT code. The model also provides a more advanced framework for understanding the underlying IA processes and their relationship to fundamental physics.

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