The dark matter assembly of the Local Group in constrained cosmological simulations of a LambdaCDM universe
The dark matter assembly of the Local Group in constrained cosmological simulations of a LambdaCDM universe
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LambdaCDM 宇宙的约束宇宙学模拟中本星系群的暗物质组装
DOI：
10.1111/j.1365-2966.2011.19358.x
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
M. Steinmetz
中科院分区：
文献类型：
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作者：
J. Forero;Y. Hoffman;G. Yepes;S. Gottlöber;R. Piontek;A. Klypin;M. Steinmetz
我们对标准LambdaCDM宇宙模型中本群（LG）的组装特性进行了详细的理论预测。我们使用了来自“线索”项目的三个宇宙学n体暗物质模拟，这些模拟旨在重现物质分布的主要动力学特征，精确到LG周围几个Mpc的尺度。此外，我们使用无约束模拟的结果，用60倍大的体积来校准宇宙方差的影响。我们用三个特征时间来描述每个光晕的质量聚集史（MAH），即形成、聚集和最后一次主要合并时间。重大合并的定义是最小质量比为10:1。我们发现这3个LGs具有相似的MAH，其形成和最后一次主要合并时代平均约在10 - 12 Gyr之前。在质量范围为5 × 10^11 Msol/h < M_h < 5 × 10^12 Msol/h的光晕中，12% ~ 17%的光晕具有相似的MAH。在相同质量范围内的一组对光晕中，1%至3%的部分与模拟LG中的两个光晕具有相似的形成特性。我们的研究结果提出了一个尚未解决的问题，即LGs毫安时的动力学起源。在无约束模拟中，通常用于定义类lg晕的隔离标准并没有将晕群缩小到具有安静mah的一组，也没有进一步的约束来驻留在低密度环境中。LGs安静的MAH为像银河系和M31这样的盘状星系的形成提供了有利的环境。银河系暗物质晕最后一次大合并的开始时间与星系盘中厚成分富含气体的合并起源相匹配。我们的研究结果支持了这样一种观点，即局部基团周围的特定大中型环境在形成其MAH和重子结构方面起着关键作用。
We make detailed theoretical predictions for the assembly properties of the Local Group (LG) in the standard LambdaCDM cosmological model. We use three cosmological N-body dark matter simulations from the CLUES project, which are designed to reproduce the main dynamical features of the matter distribution down to the scale of a few Mpc around the LG. Additionally, we use the results of an unconstrained simulation with a sixty times larger volume to calibrate the influence of cosmic variance. We characterize the Mass Aggregation History (MAH) for each halo by three characteristic times, the formation, assembly and last major merger times. A major merger is defined by a minimal mass ratio of 10:1. We find that the three LGs share a similar MAH with formation and last major merger epochs placed on average \approx 10 - 12 Gyr ago. Between 12% and 17% of the halos in the mass range 5 x 10^11 Msol/h < M_h < 5 x 10^12 Msol/h have a similar MAH. In a set of pairs of halos within the same mass range, a fraction of 1% to 3% share similar formation properties as both halos in the simulated LG. An unsolved question posed by our results is the dynamical origin of the MAH of the LGs. The isolation criteria commonly used to define LG-like halos in unconstrained simulations do not narrow down the halo population into a set with quiet MAHs, nor does a further constraint to reside in a low density environment. The quiet MAH of the LGs provides a favorable environment for the formation of disk galaxies like the Milky Way and M31. The timing for the beginning of the last major merger in the Milky Way dark matter halo matches with the gas rich merger origin for the thick component in the galactic disk. Our results support the view that the specific large and mid scale environment around the Local Group play a critical role in shaping its MAH and hence its baryonic structure at present.