Modelling the Milky Way as a dry Galaxy
Modelling the Milky Way as a dry Galaxy
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DOI：
10.1093/mnras/sty2747
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发表时间：
2018-07
影响因子：
4.8
通讯作者：
M. Fujii;Jeroen B'edorf;J. Baba;S. Zwart
中科院分区：
文献类型：
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作者：
M. Fujii;Jeroen B'edorf;J. Baba;S. Zwart
我们构建了一个模型，银河系的恒星盘和隆起嵌入在暗物质晕。所有组件被建模为$N$体系统，具有多达80亿个等质量粒子，并且集成到10\，Gyr的年龄。我们发现，自旋参数为$\lambda=0.06$的暗物质晕的净角动量需要形成一个相对较短的条（$\sim 4 $\，kpc），具有高的图案速度（40- 50\，km\，s $^{-1}$）。通过将我们的模型与银河系的观测结果进行比较，我们得出结论：盘质量为3.7\times10^{10}M_{\odot}$，初始凸起尺度长度和速度分别为1 $\，kpc和300 $\，km\，s $^{-1}$，与观测结果最吻合。盘总质量分数（$f_{\rm d}$）似乎是银河系演化的一个重要参数，并且$f_{\rm d}\sim 0.45$的模型与银河系最为相似。此外，我们在我们的模拟与银河系中的观测太阳附近的速度分布进行了比较。在我们的模拟中，观察到的速度分布的差距，这是预计由外部林德布拉德共振（所谓的大力士流），似乎是一个时间依赖性的结构。速度分布在20- 30百万年的时间尺度上变化，因此很难仅从局部速度分布的形状来估计棒的图案速度。
We construct a model for the Milky Way Galaxy composed of a stellar disc and bulge embedded in a dark-matter halo. All components are modelled as $N$-body systems with up to 8 billion equal-mass particles and integrated up to an age of 10\,Gyr. We find that net angular-momentum of the dark-matter halo with a spin parameter of $\lambda=0.06$ is required to form a relatively short bar ($\sim 4$\,kpc) with a high pattern speed (40--50\,km\,s$^{-1}$). By comparing our model with observations of the Milky Way Galaxy, we conclude that a disc mass of $\sim 3.7\times10^{10}M_{\odot}$ and an initial bulge scale length and velocity of $\sim 1$\,kpc and $\sim 300$\,km\,s$^{-1}$, respectively, fit best to the observations. The disc-to-total mass fraction ($f_{\rm d}$) appears to be an important parameter for the evolution of the Galaxy and models with $f_{\rm d}\sim 0.45$ are most similar to the Milky Way Galaxy. In addition, we compare the velocity distribution in the solar neighbourhood in our simulations with observations in the Milky Way Galaxy. In our simulations the observed gap in the velocity distribution, which is expected to be caused by the outer Lindblad resonance (the so-called Hercules stream), appears to be a time-dependent structure. The velocity distribution changes on a time scale of 20--30\,Myr and therefore it is difficult to estimate the pattern speed of the bar from the shape of the local velocity distribution alone.