Probability of Forming Gaps in the GD-1 Stream by Close Encounters of Globular Clusters
Probability of Forming Gaps in the GD-1 Stream by Close Encounters of Globular Clusters
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DOI：
10.3847/1538-4357/aca090
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Yuka Doke;Kohei Hattori
中科院分区：
文献类型：
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作者：
Yuka Doke;Kohei Hattori
GD-1 恒星流最有趣的特性之一是存在三个间隙。如果这些间隙是由与暗物质子晕的近距离接触形成的，那么 GD-1 流打开了一个令人兴奋的窗口，通过它我们可以看到银河系中暗物质子晕的大小、质量和速度分布。然而，为了使用GD-1流作为暗物质子结构的探针，我们需要证明这些间隙不是由银河系重子成分的扰动造成的。在这里，我们使用盖亚早期数据版本 3 中的 GD-1 流和 GC 的运动学数据，并充分考虑观测不确定性，进行了大量的测试粒子模拟，以研究每个已知球状星团 (GC) 形成类 GD-1 间隙的概率。我们发现，这三个间隙全部由 GC 形成的概率低至 1.7 × 10−5，并且在我们的基准模型中，由 GC 形成的间隙的预期数量仅为 0.057。我们的结果非常不利于 GC 形成间隙的情况。考虑到其他重子扰动体（例如巨型分子云）更不可能在逆行移动的 GD-1 流中形成间隙，我们得出的结论是，如果 GD-1 流中的间隙是由飞越扰动形成的，则至少有一个间隙是由暗物质子晕形成的。
One of the most intriguing properties of the GD-1 stellar stream is the existence of three gaps. If these gaps were formed by close encounters with dark matter subhalos, the GD-1 stream opens an exciting window through which we can see the size, mass, and velocity distributions of the dark matter subhalos in the Milky Way. However, in order to use the GD-1 stream as a probe of the dark matter substructure, we need to disprove that these gaps are not due to the perturbations from baryonic components of the Milky Way. Here we ran a large number of test-particle simulations to investigate the probability that each of the known globular clusters (GCs) can form a GD-1-like gap, by using the kinematical data of the GD-1 stream and GCs from Gaia early data release 3 and by fully taking the observational uncertainty into account. We found that the probability that all of the three gaps were formed by GCs is as low as 1.7 × 10−5, and the expected number of gaps formed by GCs is only 0.057 in our fiducial model. Our result highly disfavors a scenario in which GCs form the gaps. Given that other baryonic perturbers (e.g., giant molecular clouds) are even less likely to form a gap in the retrograde-moving GD-1 stream, we conclude that at least one of the gaps in the GD-1 stream was formed by dark matter subhalos if the gaps were formed by flyby perturbations.