Merger of dark matter axion clumps and resonant photon emission
Merger of dark matter axion clumps and resonant photon emission
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DOI：
10.1088/1475-7516/2020/07/067
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发表时间：
2020-05
影响因子：
6.4
通讯作者：
M. Hertzberg;Yao Li;E. D. Schiappacasse
中科院分区：
文献类型：
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作者：
M. Hertzberg;Yao Li;E. D. Schiappacasse
一部分轻标量暗物质，尤其是轴子，可能会组织成引力束缚的团块（恒星），并在今天的星系中大量存在。因此，确定这种情况是否有新的观测特征是最令人感兴趣的。研究表明，对于中等大小的轴-光子耦合，这样的团块可以经历参数共振成为光子，对于超过临界质量M -百科c的团块，我们中的一些人在参考文献[1]中精确地确定了这一点。为了在今天的星系中获得超过临界质量的团块，需要合并。在这项工作中，我们对轴子团对进行了全三维模拟，并通过发射标量波确定合并发生的条件，包括分析正面和非正面碰撞，相位依赖和相对速度。与文献中的其他工作一致，我们发现合并后的最终质量M -百科最终≈0.7（M -百科1+M -百科2）大于每个原始团块质量（对于M -百科1 ~ M -百科2）。因此，亚临界质量团块有可能合并并成为超临界，从而经历参数共振成为光子。我们发现，尽管碰撞率很小，但对于高Peccei-Quinn尺度，合并预计在今天的星系中是被运动学允许的，这是统一思想强烈建议的。由于相对速度的统计波动，较低Peccei-Quinn尺度的轴子也可能发生合并，因为它们具有较高的碰撞率。我们估计了今天银河系内部的碰撞和合并率。我们发现合并会导致地球上的能量流动，这可能是可观的，我们提到了观测搜索策略。
A portion of light scalar dark matter, especially axions, may organize into gravitationally bound clumps (stars) and be present in large number in the galaxy today. It is therefore of utmost interest to determine if there are novel observational signatures of this scenario. Work has shown that for moderately large axion-photon couplings, such clumps can undergo parametric resonance into photons, for clumps above a critical mass M⋆c determined precisely by some of us in ref. [1]. In order to obtain a clump above the critical mass in the galaxy today would require mergers. In this work we perform full 3-dimensional simulations of pairs of axion clumps and determine the conditions under which mergers take place through the emission of scalar waves, including analyzing head-on and non-head-on collisions, phase dependence, and relative velocities. Consistent with other work in the literature, we find that the final mass from the merger M⋆final≈ 0.7(M⋆1+M⋆2) is larger than each of the original clump masses (for M⋆1∼ M⋆2). Hence, it is possible for sub-critical mass clumps to merge and become super-critical and therefore undergo parametric resonance into photons. We find that mergers are expected to be kinematically allowed in the galaxy today for high Peccei-Quinn scales, which is strongly suggested by unification ideas, although the collision rate is small. While mergers can happen for axions with lower Peccei-Quinn scales due to statistical fluctuations in relative velocities, as they have a high collision rate. We estimate the collision and merger rates within the Milky Way galaxy today. We find that a merger leads to a flux of energy on earth that can be appreciable and we mention observational search strategies.