Cloud-9的冷暗物质与自相互作用暗物质解释
Cold Dark Matter and Self-Interacting Dark Matter Interpretations of Cloud-9
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中文总结 AI 辅助
研究以Cloud-9氢云为对象，用CDM和SIDM模型解释其氢柱密度轮廓，发现SIDM模型可降低与观测的张力，还在模拟中识别类似体，证实RELHIC是探测暗物质自相互作用的新探针。
中文摘要 AI 辅助
近期，五百米口径球面射电望远镜（FAST）在M94附近的21厘米波段发现了一个富含气体的氢云。由于缺乏光学对应体，这个被命名为Cloud-9的天体被认定为极具研究价值的再电离限中性氢云（RELHIC）。RELHIC为探测暗物质提供了极为纯净的实验室，不受恒星形成与反馈相关的重子复杂性影响。我们表明，Cloud-9的观测氢柱密度轮廓，既符合标准冷暗物质（CDM）模型预言的尖晕，也符合自相互作用暗物质（SIDM）产生的核晕。两种情形下，晕都必须具有异常弥散的中心密度。最佳拟合的CDM晕比宇宙学浓度-质量关系低约7σ，而SIDM形成核的晕将张力降至仅约3σ。我们还在Concerto宇宙学 zoom-in模拟套件中识别出具有速度依赖型SIDM的Cloud-9类似体，证明RELHIC是探测暗物质自相互作用的有前景的新探针。
英文摘要
Recently, the Five-hundred-meter Aperture Spherical Telescope discovered a gas-rich hydrogen cloud near M94 in the $21\,{\rm cm}$ band. Lacking an optical counterpart, this object, dubbed Cloud-9, has been identified as a compelling Reionization Limited \textsc{Hi} Cloud (RELHIC). RELHICs provide exceptionally clean laboratories for probing dark matter, free from the baryonic complexities associated with star formation and feedback. We show that the observed hydrogen column density profile of Cloud-9 is consistent with a gas cloud embedded in either a cuspy halo predicted by the standard cold dark matter (CDM) model or a cored halo produced by self-interacting dark matter (SIDM). In both cases, the halo must have an unusually diffuse central density. The best-fitting CDM halo lies around $7σ$ below the cosmological concentration--mass relation, whereas SIDM core-forming halos reduce the tension to only around $3σ$. We further identify Cloud-9 analogs in the Concerto suite of cosmological zoom-in simulations with velocity-dependent SIDM, demonstrating that RELHICs provide a promising new probe of dark matter self-interactions.
