塌陷屏障和Halo Abstract：测试偏移设置锚定器
Collapse Barriers and Halo Abundance: Testing the Excursion Set Ansatz
摘要：
我们对暗物质晕丰度的启发性理解集中在引力坍缩的密度阈值或“屏障”的概念上。如果我们采用这样的假设，即在质量尺度M上平滑的线性演化密度场的区域，其过密度超过势垒，将经历引力坍缩而形成质量为M的晕，那么这种晕的相应丰度可以简单地估计为满足坍缩判据的质量密度除以质量M的分数。因此，这个分析的关键要素是坍缩势垒作为质量M的函数，或者等价地，作为方差σ ^[2]（M）的函数的函数形式。几个这样的障碍的基础上的球形，Zel'dovich和椭球崩溃模型已被广泛讨论。使用大规模的宇宙学模拟，我们表明，线性超密度和质量方差的区域，崩溃形成晕本时代类似的期望从动力学模型的椭球崩溃之间的关系。然而，我们也表明，使用这样的崩溃障碍与偏移集animals预测晕质量函数不一致，直接在宇宙学模拟测量。这种不一致性表明，作为晕坍缩的物理模型，偏移集模型是失败的。我们讨论了我们的研究结果的影响，了解崩溃时代的晕作为质量的函数，并提高崩溃时代的分析模型和宇宙学模拟的结果之间的一致性的途径。
英文摘要：
Our heuristic understanding of the abundance of dark matter halos centers around the concept of a density threshold, or "barrier", for gravitational collapse. If one adopts the ansatz that regions of the linearly evolved density field smoothed on mass scale M with an overdensity that exceeds the barrier will undergo gravitational collapse into halos of mass M, the corresponding abundance of such halos can be estimated simply as a fraction of the mass density satisfying the collapse criterion divided by the mass M. The key ingredient of this ansatz is therefore the functional form of the collapse barrier as a function of mass M or, equivalently, of the variance sigma^2(M). Several such barriers based on the spherical, Zel'dovich, and ellipsoidal collapse models have been extensively discussed. Using large scale cosmological simulations, we show that the relation between the linear overdensity and the mass variance for regions that collapse to form halos by the present epoch resembles expectations from dynamical models of ellipsoidal collapse. However, we also show that using such a collapse barrier with the excursion set ansatz predicts a halo mass function inconsistent with that measured directly in cosmological simulations. This inconsistency demonstrates a failure of the excursion set ansatz as a physical model for halo collapse. We discuss implications of our results for understanding the collapse epoch for halos as a function of mass, and avenues for improving consistency between analytical models for the collapse epoch and the results of cosmological simulations.
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