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arXiv 1612.04041astro-ph.CO
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弱透镜峰计数宇宙学

Cosmology with weak-lensing peak counts

Chieh-An Lin

摘要:

弱引力透镜(WL)会导致星系图像的扭曲,并在大尺度上探测大质量结构,使我们能够了解宇宙的晚期演化。从WL中提取宇宙学信息的一种方法是使用峰值统计。峰是大质量晕的示踪物,因此可以探测质量函数。它们保留了非高斯信息,并且已经被证明是约束宇宙学的一个有前途的工具。在这项工作中,我们开发了一个新的模型来预测WL峰值计数。该模型基于晕圈采样生成快速模拟,并从导出的透镜映射中选择峰值。这种方法有三个主要优点。首先,该模型非常快:只需几秒钟即可执行实现。其次,包括现实条件是直截了当的。第三,由于其随机性,该模型提供了完整的分布信息。我们表明,我们的模型符合N体模拟。然后,我们研究了宇宙学相关的协方差对约束条件的影响,并探索了不同的参数推断方法。一个特别的重点放在近似贝叶斯计算(ABC),接受拒绝采样,而不需要估计的可能性。我们表明,ABC是能够产生强大的约束,大大降低了时间成本。研究了几种滤波技术,以提高多尺度信息的提取。最后,新模型被应用到CFHTLenS,KiDS DR 1/2和DES SV数据集。我们的初步结果同意普朗克约束假设的Lambda CDM模型。总体而言,本论文锻造了一个创新的工具,为未来的WL调查。该手稿对WL峰值计数进行了简要回顾。

英文摘要:

Weak gravitational lensing (WL) causes distortions of galaxy images and probes massive structures on large scales, allowing us to understand the late-time evolution of the Universe. One way to extract the cosmological information from WL is to use peak statistics. Peaks are tracers of massive halos and therefore probe the mass function. They retain non-Gaussian information and have already been shown as a promising tool to constrain cosmology. In this work, we develop a new model to predict WL peak counts. The model generates fast simulations based on halo sampling and selects peaks from the derived lensing maps. This approach has three main advantages. First, the model is very fast: only several seconds are required to perform a realization. Second, including realistic conditions is straightforward. Third, the model provides the full distribution information because of its stochasticity. We show that our model agrees well with N-body simulations. Then, we study the impacts of the cosmology-dependent covariance on constraints and explore different parameter inference methods. A special focus is put on approximate Bayesian computation (ABC), an accept-reject sampler without the need to estimate the likelihood. We show that ABC is able to yield robust constraints with much reduced time costs. Several filtering techniques are studied to improve the extraction of multiscale information. Finally, the new model is applied to the CFHTLenS, KiDS DR1/2, and DES SV data sets. Our preliminary results agree with the Planck constraints assuming the Lambda-CDM model. Overall, this thesis forges an innovative tool for future WL surveys. The manuscript provides a brief review on WL peak counts.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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