重子对直接探测暗物质的影响
The impact of baryons on the direct detection of dark matter
摘要：
银河系晕中暗物质粒子的空间和速度分布会影响在寻找暗物质时预期观察到的信号。直接探测实验的结果通常被假设为暗物质的简单等温分布，即标准晕模型（SHM）。然而，由于实际星系复杂的引力坍缩和合并历史，人们对这个简单模型的有效性持怀疑态度。在本文中，我们比较SHM的星系形成的宇宙学流体动力学模拟的结果，调查是否SHM是一个很好的代表性的真实WIMP分布的直接检测数据的分析。我们从MaGICC宇宙学模拟中研究了两个类银河星系：（a）只考虑暗物质的模拟，（b）考虑重子物理的模拟。包含重子驱动的DM晕的形状变得更加球形，并使暗物质粒子的速度分布各向异性较小，特别是在大的日心速度，从而使SHM更好地适合。我们还注意到，我们没有发现一个显着的盘状旋转暗物质组件中的两个星系晕与重子，我们检查，这表明暗盘是不是一个通用的预测宇宙流体动力学模拟。我们的结论是，在太阳附近，SHM实际上是一个很好的近似真实的暗物质分布在这些宇宙学模拟（重子），这是银河系的合理表示，因此也可以用于暗物质直接检测计算的目的。
英文摘要：
The spatial and velocity distributions of dark matter particles in the Milky Way Halo affect the signals expected to be observed in searches for dark matter. Results from direct detection experiments are often analyzed assuming a simple isothermal distribution of dark matter, the Standard Halo Model (SHM). Yet there has been skepticism regarding the validity of this simple model due to the complicated gravitational collapse and merger history of actual galaxies. In this paper we compare the SHM to the results of cosmological hydrodynamical simulations of galaxy formation to investigate whether or not the SHM is a good representation of the true WIMP distribution in the analysis of direct detection data. We examine two Milky Way-like galaxies from the MaGICC cosmological simulations (a) with dark matter only and (b) with baryonic physics included. The inclusion of baryons drives the shape of the DM halo to become more spherical and makes the velocity distribution of dark matter particles less anisotropic especially at large heliocentric velocities, thereby making the SHM a better fit. We also note that we do not find a significant disk-like rotating dark matter component in either of the two galaxy halos with baryons that we examine, suggesting that dark disks are not a generic prediction of cosmological hydrodynamical simulations. We conclude that in the Solar neighborhood, the SHM is in fact a good approximation to the true dark matter distribution in these cosmological simulations (with baryons) which are reasonable representations of the Milky Way, and hence can also be used for the purpose of dark matter direct detection calculations.
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