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arXiv 1406.4159astro-ph.CO
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宇宙网中的晕丰度

Halo abundances within the cosmic web

David Alonso, Elizabeth Eardley, John A. Peacock

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14 pages, 6 figures. Revision matching journal version
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摘要：

我们研究了在大尺度结构的宇宙网中暗物质晕的质量函数与其环境的依赖关系。晕质量函数对大尺度平均密度的依赖性是宇宙学理论的一个标准元素，它允许通过峰值-背景分裂来理解质量依赖性偏置。在高斯密度场的假设下，这种分析可以扩展到询问质量函数如何取决于几何环境：团簇、丝、片和空隙，通过潮汐张量（引力势的海森矩阵）进行分类。在线性理论中，这个问题可以精确地解决，并且结果非常简单：条件质量函数对局部潮汐场没有显式的依赖性，并且只是用于定义潮汐张量的滤波尺度上的局部密度的函数。然而，有一个很强的隐含的预测依赖于几何环境，因为局部密度耦合统计的潜在的衍生物。我们计算这个模型的预测，并研究其有效性的限制，通过比较它们的经验推导出的结果从$N$体模拟。我们已经证实，在一个很好的近似，在不同的环境中的晕的丰度只取决于它们的密度，而不是对它们的潮汐结构。在这个意义上，我们发现在不同环境中的晕丰度之间的相对差异小于13%的相同的密度。此外，对于足够大的滤波尺度，与理论预测的一致性是好的，尽管在小的非线性尺度下与高斯预测存在重要偏差。我们将讨论如何获得改进的预测，在这个政权，使用“有效宇宙”的方法。

英文摘要：

We investigate the dependence of the mass function of dark-matter haloes on their environment within the cosmic web of large-scale structure. A dependence of the halo mass function on large-scale mean density is a standard element of cosmological theory, allowing mass-dependent biasing to be understood via the peak-background split. On the assumption of a Gaussian density field, this analysis can be extended to ask how the mass function depends on the geometrical environment: clusters, filaments, sheets and voids, as classified via the tidal tensor (the Hessian matrix of the gravitational potential). In linear theory, the problem can be solved exactly, and the result is attractively simple: the conditional mass function has no explicit dependence on the local tidal field, and is a function only of the local density on the filtering scale used to define the tidal tensor. There is nevertheless a strong implicit predicted dependence on geometrical environment, because the local density couples statistically to the derivatives of the potential. We compute the predictions of this model and study the limits of their validity by comparing them to results deduced empirically from $N$-body simulations. We have verified that, to a good approximation, the abundance of haloes in different environments depends only on their densities, and not on their tidal structure. In this sense we find relative differences between halo abundances in different environments with the same density which are smaller than 13%. Furthermore, for sufficiently large filtering scales, the agreement with the theoretical prediction is good, although there are important deviations from the Gaussian prediction at small, non-linear scales. We discuss how to obtain improved predictions in this regime, using the 'effective-universe' approach.

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