Non-linear evolution of the tidal angular momentum of protostructures - II. Non-Gaussian initial conditions
Non-linear evolution of the tidal angular momentum of protostructures - II. Non-Gaussian initial conditions
复制标题
原型结构潮汐角动量的非线性演化 - II。
DOI：
--
复制
发表时间：
1997
期刊：
影响因子：
--
通讯作者：
T. Theuns
中科院分区：
文献类型：
--
作者：
P. Catelan;T. Theuns
描述弗里德曼宇宙中原结构的角动量L从潮汐力矩非线性增长的形式，如在以前的论文中所发展的，被扩展到包括非高斯初始条件。我们在此将分析局限于一类特殊的非高斯原始分布，即乘法模型。在这种模型中，强相关相位是通过高斯随机场的非线性局部变换获得引力势而产生的。利用二阶拉格朗日摄动理论描述了流体粒子的运动轨迹，分析了系统的动力学演化过程。在Einstein-de Sitter宇宙中，对于一般非高斯统计，坍缩结构的线性角动量方差的最低阶微扰修正增长为t^8/3，这与高斯统计的t^10/3增长率特性形成了对比。这是一个事实的结果，即在非高斯情况下，最低阶微扰自旋的贡献来自引力势的第三矩，这在高斯场中是相同的零。在坍缩结构的最大展开时间评估这些修正，我们发现这些非高斯和非线性项可以与线性估计一样高，而密度场的偏度和峰度量化的非高斯程度不会大得令人无法接受。结果表明，微扰膨胀中的高阶项可能对星系自旋有显著贡献，这与直接的高斯情况相反。
The formalism that describes the non-linear growth of the angular momentum L of protostructures from tidal torques in a Friedmann Universe, as developed in a previous paper, is extended to include non-Gaussian initial conditions. We restrict our analysis here to a particular class of non-Gaussian primordial distributions, namely multiplicative models. In such models, strongly correlated phases are produced by obtaining the gravitational potential via a nonlinear local transformation of an underlying Gaussian random field. The dynamical evolution of the system is followed by describing the trajectories of fluid particles using second-order Lagrangian perturbation theory. In the Einstein-de Sitter universe, the lowest-order perturbative correction to the variance of the linear angular momentum of collapsing structures grows as t^8/3 for generic non-Gaussian statistics, which contrasts with the t^10/3 growth rate characteristic of Gaussian statistics. This is a consequence of the fact that the lowest-order perturbative spin contribution in the non-Gaussian case arises from the third moment of the gravitational potential, which is identically zero for a Gaussian field. Evaluating these corrections at the maximum expansion time of the collapsing structure, we find that these non-Gaussian and non-linear terms can be as high as the linear estimate, without the degree of non-Gaussianity as quantified by skewness and kurtosis of the density field being unacceptably large. The results suggest that higher-order terms in the perturbative expansion may contribute significantly to galactic spin which contrasts with the straightforward Gaussian case.