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arXiv 1609.03576astro-ph.CO
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拉格朗日方法的性能研究:大尺度奇异速度和重子声学振荡的重建

Performance study of Lagrangian methods: reconstruction of large scale peculiar velocities and baryonic acoustic oscillations

Ariel Keselman, Adi Nusser

摘要:

NoAM是一个用于重建大尺度质量密度场示踪剂轨道的框架。它寻求运动方程(EoM)的精确解,满足初始均匀性和最终观察到的粒子(示踪剂)位置。迭代地找到的解决方案,达到指定的公差定义为重建和观察到的位置之间的距离的RMS。从对初始条件的猜测开始,NoAM使用标准的N体技术来解决EoM。可替代地,EoM可以由诸如Zel'dovich和二阶微扰理论(2LPT)的任何近似代替。NoAM适用于数十亿个粒子,可以轻松处理非规则体积,红移空间和其他约束。我们实现NoAM系统地比较Zel'dovich,2LPT,和N体动力学在不同的配置,从理想化的高分辨率周期性模拟框现实的星系模拟。我们的发现是:(i)Zel'dovich,2LPT和全动力学的非线性重建比线性理论更好地表现出理想化的目录在真实空间中。对于实际星表,线性理论是重建尺度> 5 Mpc/h的平滑速度场的最佳选择。(ii)这里测试的所有非线性时间回溯重建在关联函数中产生重子振荡信号的可比较的增强。

英文摘要:

NoAM for "No Action Method" is a framework for reconstructing the past orbits of observed tracers of the large scale mass density field. It seeks exact solutions of the equations of motion (EoM), satisfying initial homogeneity and the final observed particle (tracer) positions. The solutions are found iteratively reaching a specified tolerance defined as the RMS of the distance between reconstructed and observed positions. Starting from a guess for the initial conditions, NoAM advances particles using standard N-body techniques for solving the EoM. Alternatively, the EoM can be replaced by any approximation such as Zel'dovich and second order perturbation theory (2LPT). NoAM is suitable for billions of particles and can easily handle non-regular volumes, redshift space, and other constraints. We implement NoAM to systematically compare Zel'dovich, 2LPT, and N-body dynamics over diverse configurations ranging from idealized high-res periodic simulation box to realistic galaxy mocks. Our findings are (i) Non-linear reconstructions with Zel'dovich, 2LPT, and full dynamics perform better than linear theory only for idealized catalogs in real space. For realistic catalogs, linear theory is the optimal choice for reconstructing velocity fields smoothed on scales > 5 Mpc/h. (ii) all non-linear back-in-time reconstructions tested here, produce comparable enhancement of the baryonic oscillation signal in the correlation function.

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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