大麦云云盘成分的gamma-ray发射光谱突变的证据：强子起源？
Evidence of a spectral break in the gamma-ray emission of the disk component of Large Magellanic Cloud: a hadronic origin?
摘要：
有人认为，附近恒星形成星系的高能伽马射线发射（$>100{\rm MeV}$）可能主要是由宇宙射线通过中性π介子衰变与星际介质碰撞产生的。π介子衰变机制预测了伽马射线光谱中的独特光谱特征，其特征在于快速上升的光谱和低于几百MeV的光谱中断。本文报道了大麦云（LMC）盘辐射在500 MeV附近的光谱突变的证据，这是在分析{ \it Fermi}-大天区望远镜观测到的低至60 MeV的γ射线数据中发现的。这种破裂与γ射线发射的π介子衰变模型是一致的，尽管轻子模型，如电子韧致辐射，不能完全排除。
英文摘要：
It has been suggested that high-energy gamma-ray emission ($>100{\rm MeV}$) of nearby star-forming galaxies may be produced predominantly by cosmic rays colliding with the interstellar medium through neutral pion decay. The pion-decay mechanism predicts a unique spectral signature in the gamma-ray spectrum, characterized by a fast rising spectrum and a spectral break below a few hundreds of MeV. We here report the evidence of a spectral break around 500 MeV in the disk emission of Large Magellanic Cloud (LMC), which is found in the analysis of the gamma-ray data extending down to 60 MeV observed by {\it Fermi}-Large Area Telescope. The break is well consistent with the pion-decay model for the gamma-ray emission, although leptonic models, such as the electron bremsstrahlung emission, cannot be ruled out completely.
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