Gamma-Ray Emission from Molecular Clouds Generated by Penetrating Cosmic Rays
Gamma-Ray Emission from Molecular Clouds Generated by Penetrating Cosmic Rays
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DOI：
10.3847/1538-4357/aae827
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发表时间：
2018-12-01
影响因子：
4.9
通讯作者：
Cheng, K. S.
中科院分区：
文献类型：
--
作者：
Dogiel, V. A.;Chernyshov, D. O.;Cheng, K. S.
我们分析了控制宇宙射线（CR）穿透分子云和由此产生的伽马射线发射的过程。由于自激MHD湍流，云内CRs的密度在较低能量下被耗尽。消耗取决于云的有效气柱密度（“大小”）。我们考虑了两种不同的环境，其中预期会观察到耗竭效应。对于中心分子区，CR能量耗竭的预期范围E小于或接近10 GeV，导致E-gamma以下的伽马射线通量耗竭近似为2 GeV。这种效应对于解释银河系中心的GeV伽玛射线过剩是很重要的，这已经从CR传播的标准模型中揭示出来（假设云内的CR光谱等于星际光谱）。此外，最近对一些局部分子云的观测表明伽马射线发射耗尽，表明穿透低能cr可能存在自调制。
We analyze the processes governing cosmic-ray (CR) penetration into molecular clouds and the resulting generation of gamma-ray emission. The density of CRs inside a cloud is depleted at lower energies due to the self-excited MHD turbulence. The depletion depends on the effective gas column density ("size") of the cloud. We consider two different environments where the depletion effect is expected to be observed. For the central molecular zone, the expected range of CR energy depletion is E less than or similar to 10 GeV, leading to the depletion of gamma-ray flux below E-gamma approximate to 2 GeV. This effect can be important for the interpretation of the GeV gamma-ray excess in the Galactic Center, which has been revealed from the standard model of CR propagation (assuming the CR spectrum inside a cloud to be equal to the interstellar spectrum). Furthermore, recent observations of some local molecular clouds suggest the depletion of the gamma-ray emission, indicating possible self-modulation of the penetrating low-energy CRs.