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arXiv 1712.04461astro-ph.CO
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从非线性宇宙密度场解析推导晕质量函数

Analytic Derivation of the Halo Mass Function from the Non-Linear Cosmic Density Field

Laila Linke, Johannes Schwinn, Matthias Bartelmann

摘要:

我们估计晕质量函数(HMF)的非线性宇宙密度场应用的漂移集方法。因此,我们考虑到今天的密度分布的非高斯性,并约束独立于线性塌陷阈值$δ_{\textrm{crit}}$的HMF。如果一个球形区域的密度超过位力过密度阈值$Δ$,我们就认为它是一个晕。我们模型的非线性密度场的概率分布的高斯分布和对数正态分布的叠加,我们约束的密度波动的双谱,预测的动力学场论描述宇宙结构的形成。比较了两种不同的偏移集方法。第一种方法将密度$δ$视为平滑尺度$R$的不相关随机游走。第二个假设$δ(R)$是相关的。我们发现,如果考虑到$δ(R)$的相关性,所得到的HMF与数值模拟中发现的HMF很好地对应。此外,HMF仅微弱地依赖于密度阈值$Δ$的选择。

英文摘要:

We estimate the halo mass function (HMF) by applying the excursion set approach to the non-linear cosmic density field. Thereby, we account for the non-Gaussianity of today's density distribution and constrain the HMF independent of the linear collapse threshold $δ_{\textrm{crit}}$. We consider a spherical region as a halo, if its density today exceeds the virial overdensity threshold $Δ$. We model the probability distribution of the non-linear density field by a superposition of a Gaussian and a lognormal distribution, which we constrain with the bispectrum of density fluctuations, predicted by the kinetic field theory description of cosmic structure formation. Two different excursion set approaches are compared. The first treats the density $δ$ as an uncorrelated random walk of the smoothing scale $R$. The second assumes $δ(R)$ to be correlated. We find that the resulting HMFs correspond well to the HMF found in numerical simulations if the correlation of $δ(R)$ is taken into account. Furthermore, the HMF depends only weakly on the choice of the density threshold $Δ$.

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