The cosmic web and the orientation of angular momenta
The cosmic web and the orientation of angular momenta
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DOI：
10.1111/j.1745-3933.2012.01222.x
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发表时间：
2012-01
影响因子：
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通讯作者：
N. Libeskind;Y. Hoffman;A. Knebe;M. Steinmetz;S. Gottlober;Ofer Metuki;G. Yepes
中科院分区：
文献类型：
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作者：
N. Libeskind;Y. Hoffman;A. Knebe;M. Steinmetz;S. Gottlober;Ofer Metuki;G. Yepes
我们使用h−1 MPC纯暗物质宇宙学模拟来研究晕和子结构相对于宇宙网的大尺度取向。基于速度剪切张量的腹板分类方案被用来为模拟中的每个光晕分配一种腹板类型：结状、细丝、片状或空洞。利用质量跨越∼3个数量级的∼10 6晕，研究了晕的自旋方向和亚晕的轨道角动量相对于剪切张量的本征向量.我们发现，对于结点、细丝和片状的所有晕，亚晕的轨道角动量趋于与速度切变张量的中间本征矢对齐。这一结果表明，位于晕维化区域深处的子结构的运动学由其流入决定，而流入又由大尺度速度切变决定，这是一个令人惊讶的结果，因为晕维化的性质。因此，次晕吸积的非随机性在z=0时测量的角动量上留下了印记。我们还发现，在暗条和薄片中，晕的自旋轴与速度剪切张量的第三特征向量对齐：晕自旋轴沿暗条指向，位于宇宙薄片平面内。
We use a 64 h−1 Mpc dark-matter-only cosmological simulation to examine the large-scale orientation of haloes and substructures with respect to the cosmic web. A web classification scheme based on the velocity shear tensor is used to assign to each halo in the simulation a web type: knot, filament, sheet or void. Using ∼106 haloes that span ∼3 orders of magnitude in mass, the orientation of the halo’s spin and the orbital angular momentum of subhaloes with respect to the eigenvectors of the shear tensor is examined. We find that the orbital angular momentum of subhaloes tends to align with the intermediate eigenvector of the velocity shear tensor for all haloes in knots, filaments and sheets. This result indicates that the kinematics of substructures located deep within the virialized regions of a halo is determined by its infall which in turn is determined by the large-scale velocity shear, a surprising result given the virialized nature of haloes. The non-random nature of subhalo accretion is thus imprinted on the angular momentum measured at z= 0. We also find that the haloes’ spin axis is aligned with the third eigenvector of the velocity shear tensor in filaments and sheets: the halo spin axis points along filaments and lies in the plane of cosmic sheets.