Testing tidal-torque theory: I. spin amplitude and direction
Testing tidal-torque theory: I. spin amplitude and direction
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DOI：
10.1046/j.1365-8711.2002.05305.x
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发表时间：
2001-05
影响因子：
4.8
通讯作者：
C. Porciani;A. Dekel;Y. Hoffman
中科院分区：
文献类型：
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作者：
C. Porciani;A. Dekel;Y. Hoffman
我们评估成功的线性潮汐扭矩理论（TTT）在预测银河系晕自旋使用宇宙学N体模拟与数千个分辨率良好的晕。通过将今天的晕追溯到初始条件来识别原晕。的TTT预测的原晕相匹配，平均而言，自旋振幅的维里化的晕的今天，如果线性增长，直到2010年0/3，或55- 70%的晕有效周转时间。这使得它成为一个有用的定性工具，用于理解星系的某些平均性质，如总自旋和角动量分布在晕内，但随机散射的信号本身的顺序。自旋方向的非线性变化会导致在t0时TTT预测的平均误差为0.50 °，因此自旋在≥1 h−1 Mpc尺度上的线性空间相关性会被非线性效应显著削弱。这就质疑了TTT在引力透镜背景下预测内在排列的有用性。我们发现，在TTT的标准近似，包括二阶扩展的Zel'dovich潜在的和平滑的潮汐场，提供接近最佳的结果。
We evaluate the success of linear tidal-torque theory (TTT) in predicting galactic-halo spin using a cosmological N-body simulation with thousands of well-resolved haloes. The protohaloes are identified by tracing today's haloes back to the initial conditions. The TTT predictions for the protohaloes match, on average, the spin amplitudes of the virialized haloes of today, if linear growth is assumed until ∼t0/3, or 55–70 per cent of the halo effective turn-around time. This makes it a useful qualitative tool for understanding certain average properties of galaxies, such as total spin and angular momentum distribution within haloes, but with a random scatter of the order of the signal itself. Non-linear changes in spin direction cause a mean error of ∼50° in the TTT prediction at t0, such that the linear spatial correlations of spins on scales ≥1 h−1 Mpc are significantly weakened by non-linear effects. This questions the usefulness of TTT for predicting intrinsic alignments in the context of gravitational lensing. We find that the standard approximations made in TTT, including a second-order expansion of the Zel'dovich potential and a smoothing of the tidal field, provide close-to-optimal results.