Scale Lengths in Dark Matter Halos
Scale Lengths in Dark Matter Halos
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DOI：
10.1086/497066
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
Eric I. Barnes;L. Williams;A. Babul;J. Dalcanton
中科院分区：
文献类型：
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作者：
Eric I. Barnes;L. Williams;A. Babul;J. Dalcanton
我们调查了一个假设，关于在宇宙学N体模拟中形成的晕的尺度长度的起源。这一假说可以被看作是梅里特和阿吉拉尔提出的早期想法的延伸。我们的研究结果表明，与径向轨道不稳定性的现象是存在于这样的晕，是负责密度分布形状。这种不稳定性设置了一个尺度长度，在该尺度长度处速度色散分布从各向同性迅速变化为径向各向异性。该尺度长度在密度分布中反映为密度分布曲线改变斜率的半径。我们已经测试的想法，径向依赖的速度色散各向异性导致密度剖面形状的突破，通过操纵输入的半解析模型来模仿径向轨道不稳定性所施加的速度结构。没有这样的操作，形成的晕近似由单一的幂律密度分布和各向同性的速度分布。改变输入形成的晕显示具有尺度长度和各向异性轮廓的密度分布，类似于宇宙学N体模拟中看到的。
We investigate a hypothesis regarding the origin of the scale length in halos formed in cosmological N-body simulations. This hypothesis can be viewed as an extension of an earlier idea put forth by Merritt and Aguilar. Our findings suggest that a phenomenon related to the radial orbit instability is present in such halos and is responsible for density profile shapes. This instability sets a scale length at which the velocity dispersion distribution changes rapidly from isotropic to radially anisotropic. This scale length is reflected in the density distribution as the radius at which the density profile changes slope. We have tested the idea that radially dependent velocity dispersion anisotropy leads to a break in density profile shape by manipulating the input of a semianalytic model to imitate the velocity structure imposed by the radial orbit instability. Without such manipulation, halos formed are approximated by single power-law density profiles and isotropic velocity distributions. Halos formed with altered inputs display density distributions featuring scale lengths and anisotropy profiles similar to those seen in cosmological N-body simulations.