关于确定物质分布的形状
On determining the shape of matter distributions
摘要：
在宇宙结构形成模拟中形成的星系和晕等物体的一个基本属性是它们的形状。在这里，我们批判性地研究了文献中常用的形状确定方法。结果发现，使用一个封闭的积分体积和权重因子r^{-2}和r_{ell} ^{-2}（椭圆半径）的形状张量中的每个粒子或体积元素的贡献，导致偏轴比和平滑的细节时，计算局部形状作为一个函数的距离中心。为了确定作为良好分辨物体（通常超过O（10^4）个粒子）的距离函数的物质分布的局部形状，我们提倡一种方法，即（1）使用椭球壳（homoeoid）作为积分体积，形状张量中没有任何权重因子，（2）去除subhalos。
英文摘要：
A basic property of objects, like galaxies and halos that form in cosmological structure formation simulations, is their shape. Here, we critically investigate shape determination methods that are commonly used in the literature. It is found that using an enclosed integration volume and weight factors r^{-2} and r_{ell}^{-2} (elliptical radius) for the contribution of each particle or volume element in the shape tensor leads to biased axis ratios and smoothing of details when calculating the local shape as a function of distance from the center. To determine the local shape of matter distributions as a function of distance for well resolved objects (typically more than O(10^4) particles), we advocate a method that (1) uses an ellipsoidal shell (homoeoid) as an integration volume without any weight factors in the shape tensor and (2) removes subhalos.
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