AI 中文总结
本文探讨NGC 4945中心的神秘源“Punctum”是否为带暗物质密度尖峰的原初黑洞，发现暗物质湮灭产生的同步辐射可解释其特性，确定了相关湮灭截面与暗物质质量范围。
AI 中文摘要
近期一项研究在NGC 4945中心区域发现了一个高度偏振的毫米连续谱源，命名为“Punctum”，它不符合任何已知天体类别。除了在约100 GHz的射电探测外，在其他射电、红外、光学和X射线波段均未发现“Punctum”的对应体。所有可用的潜在模型，包括磁星、超新星遗迹和微类星体，都无法对“Punctum”表现出的约50%的极高偏振度、毫米波段光度$L_{\rm mm} \boldsymbol{\times} 10^{35}$ erg/s以及小于2 pc的小尺寸给出令人满意的解释。本文讨论了“Punctum”确实是一个带有暗物质密度尖峰的原初黑洞（PBH）的可能性。我们表明，由暗物质湮灭产生的电子和正电子引发的同步辐射可以令人满意地解释“Punctum”的观测特性，并且利用我们开发的分析框架可有效得到其湮灭截面$\boldsymbol{\times} 10^{-33}$ cm$^3$/s。此外，如果“Punctum” PBH的质量约为10-100倍太阳质量（$M_{\rm \u2609}$），则对应的暗物质质量范围为$m_{\rm DM} \boldsymbol{\times} 10-1000$ MeV。
英文摘要
A recent study has discovered a highly polarized millimeter continuum source called {\it Punctum} located at the central region of NGC 4945 which doesn't fit any known category. Apart from the radio detection at $\approx 100$ GHz, there is no identified counterpart to {\it Punctum} in other radio, infra-red, optical, and X-ray bands. All available potential models, including magnetar, supernova remnant and microquasar, cannot provide satisfactory explanation for the exceptionally high polarization of $\sim 50$\% and large luminosity in mm band $L_{\rm mm} \approx 2\times 10^{35}$ erg/s within a small size $<2$ pc shown in {\it Punctum}. In this article, we discuss the possibility that {\it Punctum} is indeed a primordial black hole (PBH) with a dark matter density spike. We show that the synchrotron radiation due to the electrons and positrons produced from dark matter annihilation can satisfactorily explain the observed properties of {\it Punctum} and we can effectively obtain the annihilation cross section $\langle σv \rangle \sim 10^{-33}$ cm$^3$/s using our developed analytic framework. Furthermore, if the {\it Punctum} PBH mass is $\sim 10-100M_{\odot}$, the preferred dark matter mass range is $m_{\rm DM} \sim 10-1000$ MeV.
