自适应网格加密模拟中的宇宙激波与宇宙射线加速
Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays
摘要：
我们提出了新的结果表征宇宙学冲击自适应网格细化N体/流体动力学模拟，用于预测非热成分的大尺度结构。这是第一次使用自适应网格细化的冲击研究。我们提出了一种改进的算法，用于从unigrid模拟中找到激波，该算法将低马赫数激波的激波频率降低了~3倍。然后，我们将我们的新技术应用于一个大的宇宙学体积（512 Mpc/h）^[3]，研究激波马赫数（M）分布作为激波前温度、密度和红移的函数。由于模拟量很大，我们有极好的统计数据，结果有成千上万的星系团。我们发现，马赫数的演变可以解释为一种方法来可视化大尺度结构的形成。马赫数小于5的激波通常跟踪合并和复杂的流动，而马赫数小于5<<20 and Mach>20的激波通常分别跟踪细丝和星系团的吸积。通过应用一阶费米过程的非线性扩散冲击加速模型的结果，我们计算了转化为宇宙线质子的动能的量。宇宙射线质子的加速度足够大，为了使用星系团作为宇宙学探测器，气体对宇宙射线的动态响应必须包括在未来的数值模拟中。
英文摘要：
We present new results characterizing cosmological shocks within adaptive mesh refinement N-Body/hydrodynamic simulations that are used to predict non-thermal components of large-scale structure. This represents the first study of shocks using adaptive mesh refinement. We propose a modified algorithm for finding shocks from those used on unigrid simulations that reduces the shock frequency of low Mach number shocks by a factor of ~3. We then apply our new technique to a large, (512 Mpc/h)^3, cosmological volume and study the shock Mach number (M) distribution as a function of pre-shock temperature, density, and redshift. Because of the large volume of the simulation, we have superb statistics that results from having thousands of galaxy clusters. We find that the Mach number evolution can be interpreted as a method to visualize large-scale structure formation. Shocks with Mach<5 typically trace mergers and complex flows, while 5<Mach<20 and Mach>20 generally follow accretion onto filaments and galaxy clusters, respectively. By applying results from nonlinear diffusive shock acceleration models using the first-order Fermi process, we calculate the amount of kinetic energy that is converted into cosmic ray protons. The acceleration of cosmic ray protons is large enough that in order to use galaxy clusters as cosmological probes, the dynamic response of the gas to the cosmic rays must be included in future numerical simulations.
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