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arXiv 1111.6629astro-ph.COastro-ph.IM
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从密度场和潮汐张量估算宇宙速度场

Estimating cosmic velocity fields from density fields and tidal tensors

Francisco-Shu Kitaura, Raul E. Angulo, Yehuda Hoffman, Stefan Gottl"ober

摘要:

本文研究了宇宙密度与奇异速度场之间的非线性、非定域关系。我们的目标是提供一种从完全非线性密度重建非线性速度场的算法。我们发现,包括引力潮汐场张量使用二阶拉格朗日微扰理论(2LPT)的基础上的非线性密度场的线性分量的估计显着改善了宇宙流的估计相比,线性理论不仅在低密度,而且更显着地在高密度区域。特别是,我们测试两个估计的线性分量:对数正态模型和迭代拉格朗日线性化。本方法依赖于严格的高阶拉格朗日微扰理论分析,其中包含非局部关系。它不需要额外的拟合模拟是在这个意义上的参数自由,它是独立的几何优化,它是简单和有效的计算。该方法被证明是产生一个无偏估计的速度场的尺度~> 5 Mpc/h与紧密高斯分布的误差。此外,特殊的速度场的发散的统计是非常好的恢复显示出良好的协议与真实的N体模拟。在高密度区域(δ > 2),在5 ~ 10 Mpc/h的尺度范围内,相对于线性理论,约10 km/s(1 sigma置信区间)的典型误差减小了80%以上。我们还发现,迭代拉格朗日线性化是显着优越的低密度制度相对于对数正态模型。

英文摘要:

In this work we investigate the nonlinear and nonlocal relation between cosmological density and peculiar velocity fields. Our goal is to provide an algorithm for the recon- struction of the nonlinear velocity field from the fully nonlinear density. We find that including the gravitational tidal field tensor using second order Lagrangian perturba- tion theory (2LPT) based upon an estimate of the linear component of the nonlinear density field significantly improves the estimate of the cosmic flow in comparison to linear theory not only in the low density, but also and more dramatically in the high density regions. In particular we test two estimates of the linear component: the log- normal model and the iterative Lagrangian linearisation. The present approach relies on a rigorous higher order Lagrangian perturbation theory analysis which incorpo- rates a nonlocal relation. It does not require additional fitting from simulations being in this sense parameter free, it is independent of statistical-geometrical optimisation and it is straightforward and efficient to compute. The method is demonstrated to yield an unbiased estimator of the velocity field on scales ~> 5 Mpc/h with closely Gaussian distributed errors. Moreover, the statistics of the divergence of the peculiar velocity field is extremely well recovered showing a good agreement with the true one from N-body simulations. The typical errors of about 10 km/s (1 sigma confidence intervals) are reduced by more than 80% with respect to linear theory in the scale range between 5 and 10 Mpc/h in high density regions (δ > 2). We also find that iterative Lagrangian linearisation is significantly superior in the low density regime with respect to the lognormal model.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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