Clumps and streams in the local dark matter distribution
Clumps and streams in the local dark matter distribution
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DOI：
10.1038/nature07153
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发表时间：
2008-08-07
期刊：
影响因子：
64.8
通讯作者：
Stadel, J.
中科院分区：
文献类型：
--
作者：
Diemand, J.;Kuhlen, M.;Stadel, J.
在冷暗物质宇宙学模型(1，2)中，结构通过较小单位的合并而形成和生长(3)。数值模拟表明，这种合并是不完整的；光晕的核心存活下来，并在其宿主(4，5)内以“次光晕”的形式绕轨道运行。在这里，我们报告了一个模拟，即使在银河晕的最里面的区域也能分辨出这样的子结构。我们在太阳圈附近发现了数百个非常集中的暗物质团，以及大量的冷流。模拟还揭示了暗物质星团的分形本质：孤立的晕和亚晕包含相同数量的子结构，并且两者的内部密度分布都是尖峰的。亚晕的内部质量和相空间密度与最近发现的暗物质占主导地位的微弱矮小卫星星系(6-8)的内部质量和相空间密度相匹配，亚晕的总体亚结构可以解释在强引力透镜中看到的异常通量比(9，10)。与光滑星系模型相比，亚晕将暗物质湮灭产生的伽马射线增加了4到15倍。当地宇宙线的产生也得到了提高，通常提高了1.4倍，但在足够接近大型次光晕的1%的地点，提高了10倍以上。(这些估计假设重子对暗物质子结构的引力效应很小。)
In cold dark matter cosmological models(1,2), structures form and grow through the merging of smaller units(3). Numerical simulations have shown that such merging is incomplete; the inner cores of haloes survive and orbit as 'subhaloes' within their hosts(4,5). Here we report a simulation that resolves such substructure even in the very inner regions of the Galactic halo. We find hundreds of very concentrated dark matter clumps surviving near the solar circle, as well as numerous cold streams. The simulation also reveals the fractal nature of dark matter clustering: isolated haloes and subhaloes contain the same relative amount of substructure and both have cusped inner density profiles. The inner mass and phase-space densities of subhaloes match those of recently discovered faint, dark-matter-dominated dwarf satellite galaxies(6-8), and the overall amount of substructure can explain the anomalous flux ratios seen in strong gravitational lenses(9,10). Subhaloes boost gamma-ray production from dark matter annihilation by factors of 4 to 15 relative to smooth galactic models. Local cosmic ray production is also enhanced, typically by a factor of 1.4 but by a factor of more than 10 in one per cent of locations lying sufficiently close to a large subhalo. (These estimates assume that the gravitational effects of baryons on dark matter substructure are small.).