arXiv 0806.42452008-06-26astro-ph

邻近星系群的动力学：宇宙学常数的作用

Dynamics of Nearby Groups of Galaxies: the role of the cosmological constant

Sébastien Peirani, José Antonio De Freitas Pacheco

备注：: 7 pages, 3 figures. Accepted for publication in A&A
发表信息：: Astron.Astrophys.488:845-851,2008
DOI：: 10.1051/0004-6361:200809711

摘要：

不同的宇宙学数据与一种被称为“暗能量”的奇异物质能量成分产生的加速膨胀相一致。宇宙学常数是一种可能性，因为它满足大多数观测约束。（目的）在这项工作中，这样的一个组件在星系群的动力学的后果进行了调查，旨在检测可能的影响，在几个百万秒差距的顺序的规模。（方法）通过引入宇宙学常数项，对Lemaintre-Tolman模型进行修正，并通过对运动方程的数值求解，得到速度-距离关系。这个关系取决于两个参数：核心质量和哈勃参数。这种关系与现有数据的非线性拟合允许获得附近五个星系群和室女星系团的质量以及哈勃常数的估计。（结果）对现有结果的分析表明，修正的Lemaintre-Tolman模型和“经典”模型的速度-距离关系与现有数据的拟合效果相当。因此，任何关于宇宙学常数在群体动力学中的作用的强有力的结论都可以成立。从目前对局部流动的研究中推导出的哈勃参数的平均值为H_0 = 65 \pm 7 km/s/Mpc。

英文摘要：

(context) Different cosmological data are consistent with an accelerated expansion produced by an exotic matter-energy component, dubbed "dark-energy''. A cosmological constant is a possibility since it satisfies most of the observational constraints. (aims) In this work, the consequences of such a component in the dynamics of groups of galaxies is investigated, aiming to detect possible effects in scales of the order of few Mpc. (methods) The Lemaître-Tolman model was modified by the inclusion of the cosmological constant term and, from the numerical solution of the equations of motion, a velocity-distance relation was obtained. This relation depends on two parameters: the central core mass and the Hubble parameter. The non-linear fit of such a relation to available data permitted to obtain masses for five nearby groups of galaxies and for the Virgo cluster as well as estimates of the Hubble constant. (results) The analysis of the present results indicates that the velocity-distance relation derived from the modified Lemaître-Tolman model as well as that derived from the "canonical'' model give equally acceptable fits to the existent data. As a consequence, any robust conclusion on the effects of the cosmological constant in the dynamics of groups could be established. The mean value of the Hubble parameter derived from the present study of local flows is H_0 = 65\pm 7 km/s/Mpc.

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