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arXiv 1209.2126astro-ph.GA
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用冷潮汐流测量银河势和检验重力的统计方法

A statistical method for measuring the Galactic potential and testing gravity with cold tidal streams

Jorge Peñarrubia, Sergey E. Koposov, Matthew G. Walker

摘要:

我们介绍了最小熵方法,一个简单的统计技术,约束银河系引力势,同时测试不同的引力理论直接从6D相空间调查,而不采用动力学模型。我们证明,轨道能量分布是可分离的(即独立的位置)有一个相关的熵,增加错误的假设下的引力势和/或引力理论。在已知的天体中,来自低质量祖先的“冷”潮汐流遵循最接近满足可分离性条件的轨道分布。虽然潮汐剥离的恒星的轨道是由祖先的自重扰动,系统的能量分布的变化可以量化的交叉熵的个别尾巴,给予进一步的敏感性,在主机潜在的理论偏差。使用最小熵方法来测试范围广泛的引力理论的可行性,通过在牛顿势中发展限制N体模型和检查由Dirac,MONDian和f(R)引力修正引入的熵的变化来说明。

英文摘要:

We introduce the Minimum Entropy Method, a simple statistical technique for constraining the Milky Way gravitational potential and simultaneously testing different gravity theories directly from 6D phase-space surveys and without adopting dynamical models. We demonstrate that orbital energy distributions that are separable (i.e. independent of position) have an associated entropy that increases under wrong assumptions about the gravitational potential and/or gravity theory. Of known objects, `cold' tidal streams from low-mass progenitors follow orbital distributions that most nearly satisfy the condition of separability. Although the orbits of tidally stripped stars are perturbed by the progenitor's self-gravity, systematic variations of the energy distribution can be quantified in terms of the cross-entropy of individual tails, giving further sensitivity to theoretical biases in the host potential. The feasibility of using the Minimum Entropy Method to test a wide range of gravity theories is illustrated by evolving restricted N-body models in a Newtonian potential and examining the changes in entropy introduced by Dirac, MONDian and f(R) gravity modifications.

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