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arXiv 1111.5616astro-ph.CO
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暗物质晕的排列和排列

The Shapes and Alignments of Dark Matter Halos

Michael D. Schneider, Carlos S. Frenk, Shaun Cole

摘要:

我们目前的测量三轴暗物质晕的形状和对齐关联函数的千年和千年-2暗物质N体模拟。这两个模拟使我们能够在6 E9 - 2 E14 Msun/h的晕质量范围内测量低至维里半径10%的晕形状分布。我们在很大程度上证实了以前的结果晕轴比的分布作为晕质量的函数,但我们发现,在不同的晕半径晕主轴之间的中位角可以变化的千年-1和2模拟之间的一个因素,因为不同的质量分辨率。因此,在有限的分辨率的形状确定的错误是潜在的退化与晕的内部和外部形状的不一致,用于约束Brilliant星团星系的路线在以前的作品。我们还提出了简化参数化的3-D晕-质量排列关联函数,这是必要的成分,三轴晕模型的大尺度结构和模型的星系固有的路线作为污染物的宇宙剪切调查。我们测量所有质量的晕和周围的暗物质overdensities到几十Mpc/h之间的强烈对齐,与观察到的剪切星系和集群形状的相关性。我们利用这些测量结果来预测沿视线方向的相关质量对星系团周围弱透镜信号的贡献。对于长轴与视线对准的长轴星系团,从质量外部到星系团的弱透镜信号的分数可以是预测的两倍,如果过量晕对准相关性假设为零。

英文摘要:

We present measurements of the triaxial dark matter halo shapes and alignment correlation functions in the Millennium and Millennium-2 dark matter N-body simulations. These two simulations allow us to measure the distributions of halo shapes down to 10% of the virial radius over a halo mass range of 6E9 - 2E14 M_sun/h. We largely confirm previous results on the distributions of halo axis ratios as a function of halo mass, but we find that the median angle between halo major axes at different halo radii can vary by a factor of 2 between the Millennium-1 and 2 simulations because of the different mass resolution. Thus, error in the shape determinations from limited resolution is potentially degenerate with the misalignment of halo inner and outer shapes used to constrain Brightest Cluster Galaxy alignments in previous works. We also present simplifying parameterizations for the 3-D halo-mass alignment correlation functions that are necessary ingredients for triaxial halo models of large-scale structure and models of galaxy intrinsic alignments as contaminants for cosmic shear surveys. We measure strong alignments between halos of all masses and the surrounding dark matter overdensities out to several tens of Mpc/h, in agreement with observed shear-galaxy and cluster shape correlations. We use these measurements to forecast the contribution to the weak lensing signal around galaxy clusters from correlated mass along the line-of-sight. For prolate clusters with major axes aligned with the line-of-sight the fraction of the weak lensing signal from mass external to the cluster can be twice that predicted if the excess halo alignment correlation is assumed to be zero.

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