费米大面积望远镜在 Westerlund 1 大质量星团和 Kes 41 超新星遗迹附近看到的扩展伽马射线发射
Extended gamma-ray emission in the vicinity of the Westerlund 1 massive star cluster and Kes 41 supernova remnant seen by the Fermi Large Area Telescope
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- Univ Toulouse, CNES, CNRS, IRAP（图卢兹大学，法国国家空间研究中心，法国国家科学研究中心，天体物理研究所）
- Institut Supérieur de l’Aéronautique et de l’Espace (ISAE-Supaero)（高级航空与航天学院）
- Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）
- Université Bordeaux, CNRS, LP2I Bordeaux, UMR 5797（波尔多大学，法国国家科学研究中心，波尔多强相互作用与粒子物理研究所）
- INAF Osservatorio Astrofisico Arcetri（意大利国家天体物理研究所阿切特里天文台）
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中文总结 AI 辅助
利用费米LAT数据，在Westerlund 1星团和Kes 41超新星遗迹附近发现三个扩展伽马射线发射成分，支持中间尺度发射结构的存在。
中文摘要 AI 辅助
越来越多的证据表明，在大质量星团中存在宇宙射线加速现象。此外，扩展伽马射线发射表明，在其源附近的粒子输运受到与银河系中大尺度扩散明显不同的物理过程的影响。我们利用费米大面积望远镜（LAT）超过16年的数据，在能量大于0.8 GeV 的条件下，刻画了 Westerlund 1 星团和 Kes 41 超新星遗迹方向上的扩展伽马射线发射。我们检验了与多波长对应体无关的伽马射线源团是否更适合用扩展发射成分来描述。我们报告了在银道面高气体柱密度区域探测到三个具有软谱的新的扩展发射成分。其中一个与 Kes 41 的诞生云相关的扩展成分在统计上优于先前针对该超新星遗迹壳层报告的点源。另外两个扩展成分与 Westerlund 1 超级气泡边缘约100 pc 内的中性气体重叠。扩展发射可能由星际背景模型中气体建模不当或粒子的局部注入来解释。在后一种假设下，解释与 Kes 41 相关的成分需要将超新星遗迹能量的约5%以下转化为加速粒子，而解释 Westerlund 1 附近的两个成分则需要将星团风机械功率的10^-4转化为伽马射线。尽管如此，我们的结果加强了在孤立天体与星际介质大尺度弥散发射之间的中间空间尺度上出现伽马射线发射结构的证据。这可能解释费米 LAT 探测到的部分软谱未关联银河系源。（删节）
英文摘要
There is growing evidence for cosmic-ray acceleration in massive stellar clusters. Furthermore, extended gamma-ray emission suggests that particle transport in the vicinity of their sources is influenced by physical processes markedly different from large-scale diffusion in the Milky Way. We characterize extended gamma-ray emission in the direction of the Westerlund 1 stellar cluster and Kes 41 supernova remnant using > 16 years of data from the Fermi Large Area Telescope (LAT) at energies > 0.8 GeV. We test whether clusters of gamma-ray sources not associated to multiwavelength counterparts are better described by extended emission components. We report the detection of three new extended emission components with soft spectra towards regions of high gas column density in the Galactic plane. One extended component associated with the natal cloud of Kes 41 is statistically preferred over the point source previously reported towards the supernova remnant shell. The other two extended components overlap with neutral gas within ~100 pc from the edge of the Westerlund 1 superbubble. The extended emission may be explained either by mismodeled gas in the interstellar background model or by the local injection of particles. Under the latter hypothesis, explaining the component associated with Kes 41 requires converting $\lesssim 5\%$ of the supernova remnant energy into accelerated particles, while accounting for the two components near Westerlund 1 requires converting $10^{-4}$ of the cluster wind mechanical power into gamma rays. Nevertheless, our results strengthen the evidence for gamma-ray emission structures arising at intermediate spatial scales between isolated objects and the large-scale diffuse emission from the interstellar medium. This could explain a part of the soft unassociated Galactic sources detected by the Fermi LAT. (Abridged)
