标题： 在增长的冷暗物质晕中的焦散线 显示英文标题

标题： Caustics in growing Cold Dark Matter Haloes

摘要： 我们从自相似和球对称的初始条件出发，模拟孤立暗物质晕的增长。 我们的N体代码通过求解测地线偏差方程，以追踪与单个模拟粒子相关的流和奇点。 径向轨道不稳定性导致我们的晕在内部区域发展出接近10:1的主要轴与次要轴比。 它们随时间增长的方式相似，并且具有与球形相似解类似的密度分布，但其详细结构却大不相同。 轨道的高维性导致它们的流和奇点密度比相似解中的下降得更快。 这导致每个点处的流数量相应增加。 在回转半径的1%（大致对应于银河系中太阳的位置）处，我们的模拟中大约有10^6条流，而相似解中只有10^2条。 内晕中的奇点数量增加了几倍，因为典型轨道有六个转折点而不是一个，但奇点密度下降的幅度要大得多。 这减少了奇点对湮灭辐射的贡献。 在回转半径的1%到50%之间的区域，这在我们模拟的晕中占总值的4%，而在相似解中占6.5%。 在更小的半径处，奇点的贡献要少得多。 这些数值假设的是一个100 GeV c^-2的中性子，当前速度弥散度为0.03 cm s^-1，但将弥散度减少十个数量级只会使奇点亮度翻倍。 我们得出结论，奇点在晕的内部区域将无法观测到。 只有最外层的奇点可能有被探测到的潜力。 显示英文摘要

摘要： We simulate the growth of isolated dark matter haloes from self-similar and spherically symmetric initial conditions. Our N-body code integrates the geodesic deviation equation in order to track the streams and caustics associated with individual simulation particles. The radial orbit instability causes our haloes to develop major-to-minor axis ratios approaching 10 to 1 in their inner regions. They grow similarly in time and have similar density profiles to the spherical similarity solution, but their detailed structure is very different. The higher dimensionality of the orbits causes their stream and caustic densities to drop much more rapidly than in the similarity solution. This results in a corresponding increase in the number of streams at each point. At 1% of the turnaround radius (corresponding roughly to the Sun's position in the Milky Way) we find of order 10^6 streams in our simulations, as compared to 10^2 in the similarity solution. The number of caustics in the inner halo increases by a factor of several, because a typical orbit has six turning points rather than one, but caustic densities drop by a much larger factor. This reduces the caustic contribution to the annihilation radiation. For the region between 1% and 50% of the turnaround radius, this is 4% of the total in our simulated haloes, as compared to 6.5% in the similarity solution. Caustics contribute much less at smaller radii. These numbers assume a 100 GeV c^-2 neutralino with present-day velocity dispersion 0.03 cm s^-1, but reducing the dispersion by ten orders of magnitude only doubles the caustic luminosity. We conclude that caustics will be unobservable in the inner parts of haloes. Only the outermost caustic might potentially be detectable.