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arXiv 1608.00971astro-ph.GA
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Milky Way的质量分布和引力势

The mass distribution and gravitational potential of the Milky Way

Paul J. McMillan

摘要:

我们提出了银河系的质量模型,以适应观测的限制,并与理论建模的预期一致。用于创建这些模型的方法是在McMillan(2011)中演示的,我们通过将气体盘添加到势中来改进这些模型,考虑允许晕密度分布的内斜率变化的影响,并在新的约束条件中包括对银河系中脉泽源的新观测。我们提供了一个最佳拟合模型,以及估计的银河系的属性。在我们的主要模型的假设下,我们发现太阳是从银河系中心出发的$R_0 = (8.20\pm0.09)\,\mathrm{kpc}$,太阳的圆周速度是$v_0 = (232.8\pm3.0)\,\mathrm{km}\,\mathrm{s}^{-1}$ ;银河系的恒星总质量是$(54.3\pm5.7)\times10^9\,{\rm M}_\odot$,总维里质量是$(1.30 \pm 0.30)\times10^{12}\,{\rm M}_\odot$,局部暗物质密度是$0.38\pm0.04\,\mathrm{GeV\,cm}^{-3}$,这里引用的不确定性是统计的。这些值对我们的先验和约束的选择很敏感。我们调查系统的不确定性,在某些情况下可能会更大。例如,如果我们削弱$R_0$的先验,我们会发现它是$(7.97\pm0.15)\,\mathrm{kpc}$,而$v_0=(226.8\pm4.2)\,\mathrm{km}\,\mathrm{s}^{-1}$。我们发现,大多数这些属性,包括当地的暗物质密度,是显着不敏感的假设幂律密度斜率在暗物质晕的中心。我们发现,这是不太可能的地方标准的休息显着不同的轴对称假设下发现。我们已经编写了代码,可以从我们的势能计算力,并在其中整合轨道,公开可用。

英文摘要:

We present mass models of the Milky Way created to fit observational constraints and to be consistent with expectations from theoretical modelling. The method used to create these models is that demonstrated in McMillan (2011), and we improve on those models by adding gas discs to the potential, considering the effects of allowing the inner slope of the halo density profile to vary, and including new observations of maser sources in the Milky Way amongst the new constraints. We provide a best fitting model, as well as estimates of the properties of the Milky Way. Under the assumptions in our main model, we find that the Sun is $R_0 = (8.20\pm0.09)\,\mathrm{kpc}$ from the Galactic Centre, with the circular speed at the Sun being $v_0 = (232.8\pm3.0)\,\mathrm{km}\,\mathrm{s}^{-1}$; that the Galaxy has a total stellar mass of $(54.3\pm5.7)\times10^9\,{\rm M}_\odot$, a total virial mass of $(1.30 \pm 0.30)\times10^{12}\,{\rm M}_\odot$ and a local dark-matter density of $0.38\pm0.04\,\mathrm{GeV\,cm}^{-3}$, where the quoted uncertainties are statistical. These values are sensitive to our choice of priors and constraints. We investigate systematic uncertainties, which in some cases may be larger. For example, if we weaken our prior on $R_0$, we find it to be $(7.97\pm0.15)\,\mathrm{kpc}$ and that $v_0=(226.8\pm4.2)\,\mathrm{km}\,\mathrm{s}^{-1}$. We find that most of these properties, including the local dark-matter density, are remarkably insensitive to the assumed power-law density slope at the centre of the dark-matter halo. We find that it is unlikely that the local standard of rest differs significantly from that found under assumptions of axisymmetry. We have made code to compute the force from our potential, and to integrate orbits within it, publicly available.

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