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arXiv 1003.4544astro-ph.CO
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在MareNostrum宇宙中的强透镜作用:在星团透镜群中的偏差

Strong lensing in the MareNostrum Universe: biases in the cluster lens population

Massimo Meneghetti, Cosimo Fedeli, Francesco Pace, Stefan Gottloeber, Gustavo Yepes

摘要:

强透镜效应是研究星系团内部质量分布最直接的方法之一。它可以用来约束密度分布和测量透镜的质量。此外,强透镜事件的丰度可以用来约束结构的形成和宇宙学参数通过所谓的“弧统计”的方法。然而,在宇宙学应用中与强透镜团簇的使用相关的几个问题仍然存在争议,导致怀疑一些偏见可能会影响这类非常特殊的物体。通过这项研究,我们的目标是更好地了解星系团的性质,这可能是强透镜。我们这样做是通过调查的N体/流体动力学模拟MareNostrum宇宙提取的大样本的星系团的属性。我们探讨了透镜效应的截面与星系团的质量、三维形状、投影形状、浓度、X射线光度和动力学活动等性质之间的关系。我们发现,透镜的主轴和视线之间的强对准的概率是透镜截面的增长函数。在投影中,强透镜在R200内看起来更圆,但我们发现,随着透镜截面的增加,它们的核心往往更椭圆。我们还发现,从预计的密度分布估计的集群浓度往往偏高。强透镜星系团的X射线光度比类似质量和红移的正常透镜团的高。这对于质量最小的透镜尤其重要。最后,我们发现,最强的透镜通常表现出过剩的动能的维里半径内,这表明他们是更动态活跃比通常的集群。

英文摘要:

Strong lensing is one of the most direct probes of the mass distribution in the inner regions of galaxy clusters. It can be used to constrain the density profiles and to measure the mass of the lenses. Moreover, the abundance of strong lensing events can be used to constrain the structure formation and the cosmological parameters through the so-called "arc-statistics" approach. However, several issues related to the usage of strong lensing clusters in cosmological applications are still controversial, leading to the suspect that several biases may affect this very peculiar class of objects. With this study we aim at better understanding the properties of galaxy clusters which can potentially act as strong lenses. We do so by investigating the properties of a large sample of galaxy clusters extracted from the N-body/hydrodynamical simulation MareNostrum Universe. We explore the correlation between the cross section for lensing and many properties of clusters, like the mass, the three-dimensional and projected shapes, their concentrations, the X-ray luminosity and the dynamical activity. We find that the probability of strong alignments between the major axes of the lenses and the line of sight is a growing function of the lensing cross section. In projection, the strong lenses appear rounder within R200, but we find that their cores tend to be more elliptical as the lensing cross section increases. We also find that the cluster concentrations estimated from the projected density profiles tend to be biased high. The X-ray luminosity of strong lensing clusters is higher than that of normal lenses of similar mass and redshift. This is particular significant for the least massive lenses. Finally, we find that the strongest lenses generally exhibit an excess of kinetic energy within the virial radius, indicating that they are more dynamically active than usual clusters.

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