M31和Milky Way周围的巨大cosmic ray光环
Giant cosmic ray halos around M31 and the Milky Way
摘要：
最近，从仙女座方向探测到了1-100 GeV $γ$射线的扩散发射。辐射以星系为中心，并延伸到距离中心$\sim 100-200$千秒差距的地方。在注入银盘或银河系中心的宇宙射线逃逸的标准情景框架内解释扩展的$γ-$射线发射是有问题的。在本文中，我们认为，宇宙射线的起源（无论是轻子或强子）的$γ$射线发射是可能的非标准的宇宙射线传播的框架方案或在粒子加速发生在星系的晕的情况下。这意味着在M31周围存在一个巨大的宇宙射线晕，可能是由星系核活动或星系际气体的吸积提供动力。值得注意的是，如果像在M31周围观察到的那样，宇宙射线晕是星系的共同特征，包括我们自己的星系，宇宙射线质子和银河系环星系气体之间的相互作用也可以解释冰立方观测到的中微子的各向同性扩散通量。
英文摘要：
Recently, a diffuse emission of 1-100 GeV $γ$-rays has been detected from the direction of Andromeda. The emission is centered on the galaxy, and extends for $\sim 100-200$ kpc away from its center. Explaining the extended $γ-$ray emission within the framework of standard scenarios for the escape of cosmic rays injected in the galactic disk or in the galactic center is problematic. In this paper, we argue that a cosmic ray origin (either leptonic or hadronic) of the $γ$-ray emission is possible in the framework of non standard cosmic ray propagation scenarios or in the case of particle acceleration taking place in the galaxy's halo. It would imply the existence of a giant cosmic ray halo surrounding M31, possibly powered by the galaxy nuclear activity, or by accretion of intergalactic gas. Remarkably, if cosmic ray halos, as the one observed around M31, are a common feature of galaxies, including our own, the interactions between cosmic ray protons and the Milky Way circumgalactic gas could also explain the isotropic diffuse flux of neutrinos observed by Icecube.
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