The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ~2400 SDSS Blue Horizontal-Branch Stars
The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ~2400 SDSS Blue Horizontal-Branch Stars
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DOI：
10.1086/589500
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发表时间：
2008-01
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影响因子：
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通讯作者：
X. Xue;X. Xue;H. Rix;Gang Zhao;P. Fiorentin;P. Fiorentin;T. Naab;Matthias Steinmetz;F. C. V. D
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文献类型：
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作者：
X. Xue;X. Xue;H. Rix;Gang Zhao;P. Fiorentin;P. Fiorentin;T. Naab;Matthias Steinmetz;F. C. V. D
我们推导出新的限制银河系的暗物质晕的质量，根据2401严格选择蓝色水平分支晕星SDSS DR 6。这个例子可以在不同的银河系中心半径的完整的视线速度分布的建设。为了解释这些分布，我们将它们与来自两个不同宇宙学星系形成模拟的匹配模拟观测进行比较，这些模拟观测旨在模拟银河系。这一过程的结果是银河系的圆周速度曲线估计为~60 kpc，这比太阳位置的220 km s−1略有下降，意味着M（< 60 kpc）=（4.0 ± 0.7）× 1011 M。Vcir（r）的径向依赖性，在统计上独立的仓，来自NFW暗物质晕与建立恒星质量分量在其中心的预期是一致的。如果我们假设NFW晕的特征浓度分布成立，我们可以利用观测结果来估计银河系暗物质晕的维里质量，Mvir = 1.0+ 0.3−0.2 × 1012 M，这比许多以前的估计要低。我们已经检查过，宇宙学模拟的细节不太可能引入比统计不确定性更大的系统学。这一估计意味着银河系暗物质晕维里半径内近40%的重子存在于我们银河系的恒星组成部分中。Mvir的值仅为~1 × 1012 M，这也（重新）提出了银河系所有卫星星系是否都在束缚轨道上的问题。
We derive new constraints on the mass of the Milky Way’s dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way’s circular velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s−1 at the Sun’s location, and implies M(< 60 kpc) = (4.0 ± 0.7) × 1011 M☉. The radial dependence of Vcir(r) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way’s dark matter halo, Mvir = 1.0+ 0.3−0.2 × 1012 M☉, which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way’s dark matter halo reside in the stellar components of our Galaxy. A value for Mvir of only ~1 × 1012 M☉ also (re)opens the question of whether all of the Milky Way’s satellite galaxies are on bound orbits.