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arXiv 2406.04087astro-ph.HE
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年轻大质量星团对银河弥散γ射线辐射的贡献

Contribution of young massive star clusters to Galactic diffuse $γ$-ray emission

Stefano Menchiari, Giovanni Morlino, Elena Amato, Niccolò Bucciantini, Giada Peron, Germano Sacco

AI总结:

本文基于局地年轻大质量星团性质构建合成族群,模拟其集体星风终止激波加速宇宙线产生的强子型γ射线,指出未分辨星团尤其在内银河显著贡献弥散辐射。

摘要:

背景:年轻大质量星团(YMSCs)已成为潜在的γ射线源,此前已有约十二个YMSCs与延展γ射线辐射相关联。探测到的晕尺度很大,与YMSCs周围预期存在的星风吹出泡尺度相当,这使得单个YMSC的γ射线探测颇具挑战。因此,银河系中大多数YMSCs的辐射可能未被分辨,从而促成沿银道面观测到的弥散γ射线辐射。目的:在本研究中,我们估算由一个YMSCs合成族群对银河弥散γ射线辐射可能作出的贡献,并在银道面的两个区域内,将其与不同实验在1 GeV至数百TeV范围内获得的观测结果进行比较。方法:由于银河系YMSCs族群目前仅在局地得到认识,我们依据局地星团的观测性质模拟YMSCs合成族群,并据此评估γ射线辐射贡献。我们计算每个星团的γ射线辐射,假设该辐射本质上完全是强子型的,并由在星团集体星风终止激波处加速的宇宙线产生。结果:我们发现,未被分辨的YMSCs所产生的γ射线辐射可对观测到的银河弥散通量作出显著贡献,尤其是在银河系内部;Wolf-Rayet星风注入的功率发挥了重要作用。鉴于我们的计算忽略了在YMSCs中爆发的超新星的贡献,预测的γ射线通量应被视为下限。

英文摘要:

Context: Young massive stellar clusters (YMSCs) have emerged as potential $γ$-ray sources, after the recent association of a dozen YMSCs with extended $γ$-ray emission. The large size of the detected halos, comparable to that of the wind-blown bubble expected around YMSCs, makes the $γ$-ray detection of individual YMSCs rather challenging. As a result, the emission from most of the Galactic YMSCs could be unresolved, thus contributing to the diffuse $γ$-ray radiation observed along the Galactic Plane. Aims: In this study, we estimate the possible contribution to the Galactic diffuse $γ$-ray emission from a synthetic population of YMSCs, and we compare it with observations obtained with different experiments, from 1 GeV to hundreds of TeV, in two regions of the Galactic Plane. Methods: As the population of galactic YMSCs is only known locally, we evaluate the contribution of $γ$-ray emission relying on the simulation of synthetic populations of YMSCs based on the observed properties of local clusters. We compute the $γ$-ray emission from each cluster assuming that the radiation is purely hadronic in nature and produced by cosmic rays accelerated at the cluster's collective wind termination shock. Results: We find that the $γ$-ray emission from unresolved YMSCs can significantly contribute to the observed Galactic diffuse flux, especially in the inner part of the Galaxy, and that an important role is played by the power injected by Wolf-Rayet stellar winds. The predicted $γ$-ray flux should be considered as a lower limit, given that our calculation neglects the contribution of supernovae exploding in YMSCs.

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