Ultra-high-energy (UHE, >0.1 PeV) γ-ray astronomy is rapidly evolving into an expanding branch of γ-ray astronomy with the surprising discovery of 12 PeVatrons and the detection of a handful of photons above 1 PeV. Nearly all known celestial object types that have emissions in the TeV band are found also to emit UHE photons. UHE γ-rays have a well-defined horizon inside our Galaxy due to the absorption of infrared and cosmic microwave backgrounds in the Universe. In the last 30 years, traditional cosmic ray (CR) measurement techniques have enabled the detection of UHE γ-rays and opened the last observation window. For leptonic sources, UHE radiation is in the deep Klein–Nishina regime, which is largely suppressed. Therefore, UHE γ-ray detection will be helpful in locating and identifying hadronic radiation sources, tracing the historic pursuit for the origin of CRs around the knee of the spectrum. The Crab Nebula is the focus of attention with measured photon emissions up to 1 PeV. In the absence of hadronic processes, these emissions may indicate the existence of an extreme accelerator of e+ e−. Use of CR extensive air shower detection techniques broadens the field of view of the source observations, enabling measurement of UHE radiation surrounding the sources. These observations can probe the particle propagation inside and outside the accelerators and the subsequent injection/escape into the interstellar medium.

中文翻译：

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超高能伽马射线天文学


超高能 （UHE， >0.1 PeV） γ射线天文学正在迅速发展成为γ射线天文学的一个扩展分支，令人惊讶地发现了 12 个 PeVatron 并探测到少数高于 1 PeV 的光子。几乎所有已知的在 TeV 波段发射的天体类型也都发射 UHE 光子。由于吸收了宇宙中的红外和宇宙微波背景，UHE γ射线在我们的银河系中具有明确的视界。在过去的 30 年里，传统的宇宙射线 （CR） 测量技术使 UHE γ射线的探测成为可能，并打开了最后的观察窗口。对于轻子源，UHE 辐射处于较深的 Klein-Nishina 状态，该状态在很大程度上受到抑制。因此，UHE γ射线检测将有助于定位和识别强子辐射源，追溯对光谱拐点周围CR起源的历史追求。蟹状星云是人们关注的焦点，测得的光子发射高达 1 PeV。在没有强子过程的情况下，这些发射可能表明存在 e+ e− 的极端加速器。使用 CR 广泛的空气淋浴检测技术拓宽了源观测的视野，从而能够测量源周围的 UHE 辐射。这些观测可以探测粒子在加速器内外的传播，以及随后注入/逃逸到星际介质中。