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arXiv 1507.03643astro-ph.GA
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APOSTLE项目:Local Group运动质量约束和模拟候选选择

The APOSTLE project: Local Group kinematic mass constraints and simulation candidate selection

Azadeh Fattahi, Julio F. Navarro, Till Sawala, Carlos S. Frenk, Kyle A. Oman, Robert A. Crain, Michelle Furlong, Matthieu Schaller, Joop Schaye, Tom Theuns, Adrian Jenkins

摘要:

我们使用一个大样本的孤立的暗物质晕对宇宙学N体模拟,以确定候选系统的运动学匹配的本地集团的Galerkin(LG)。我们发现,在协议的“时间参数”和早期的工作,银河系(MW)和仙女座(M31)星系的分离和方法的速度有利于总质量对$\sim 5\times 10^{12} \,M_{\odot}$。然而,如此大的质量很难与这对小的相对切向速度相一致,也很难与哈勃流对最远的LG成员观察到的小减速相一致。符合这三个标准的晕对的平均质量比时间论证所建议的小$\sim 2$倍,但分散度很大。在这些结果的指导下,我们选择了$12$晕对的总质量范围$1.6$ - $3.6 \times 10^{12}\,M_{\odot}$的APOSTLE项目(一个项目的模拟本地环境),一套流体动力学reimulations在各种数值分辨率水平(达到$\sim10^{4}\,M_{\odot}$每个气体粒子),使用的次网格物理为EAGLE项目开发。这些模拟再现,通过建设,主要的运动学的MW-M31对,并产生卫星人口的总体数量,光度和运动学是在良好的协议与观察MW和M31同伴。因此,APOSTLE候选系统提供了一个很好的试验平台,可以直接面对$Λ$ CDM宇宙学的许多预测与我们本地宇宙的观测。

英文摘要:

We use a large sample of isolated dark matter halo pairs drawn from cosmological N-body simulations to identify candidate systems whose kinematics match that of the Local Group of Galaxies (LG). We find, in agreement with the "timing argument" and earlier work, that the separation and approach velocity of the Milky Way (MW) and Andromeda (M31) galaxies favour a total mass for the pair of $\sim 5\times 10^{12} \,M_{\odot}$. A mass this large, however, is difficult to reconcile with the small relative tangential velocity of the pair, as well as with the small deceleration from the Hubble flow observed for the most distant LG members. Halo pairs that match these three criteria have average masses a factor of $\sim 2$ times smaller than suggested by the timing argument, but with large dispersion. Guided by these results, we have selected $12$ halo pairs with total mass in the range $1.6$-$3.6 \times 10^{12}\,M_{\odot}$ for the APOSTLE project (A Project Of Simulating The Local Environment), a suite of hydrodynamical resimulations at various numerical resolution levels (reaching up to $\sim10^{4}\,M_{\odot}$ per gas particle) that use the subgrid physics developed for the EAGLE project. These simulations reproduce, by construction, the main kinematics of the MW-M31 pair, and produce satellite populations whose overall number, luminosities, and kinematics are in good agreement with observations of the MW and M31 companions. The APOSTLE candidate systems thus provide an excellent testbed to confront directly many of the predictions of the $Λ$CDM cosmology with observations of our local Universe.

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