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arXiv 1608.01587astro-ph.HE
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Milky Way对超高能γ射线的吸收

Absorption of Very High Energy Gamma Rays in the Milky Way

Silvia Vernetto, Paolo Lipari

摘要:

银河系极高能(E > 30 TeV)γ射线天文学是研究非热宇宙的重要工具。在这个能量区域的观测的解释需要对由于对生产相互作用的光子衰减的精确建模,其中的目标是星际空间中存在的辐射场。对于能量E > 300 TeV的γ射线,衰减主要是由于宇宙微波背景辐射(CMBR)的光子。在较低的能量下,最重要的目标是尘埃发射的波长在50-500微米范围内的红外光子。衰减的评估需要对银河系中所有位置的目标光子的密度、能量和角分布有很好的了解。在这项工作中,我们讨论了一个简单的红外辐射模型,它只依赖于与发射尘埃的空间和温度分布相关的几个参数。该模型允许计算具有良好的精度的任何空间和能量分布的扩散银河伽马射线辐射的吸收的影响。由于银河系红外辐射的吸收概率是最大的E约150 TeV,并可以大到P_abs约0.45的视线上通过靠近银河系中心的遥远的来源。吸收概率的系统不确定度估计为Δ P_abs < 0.08。

英文摘要:

Galactic Gamma ray astronomy at very high energy (E > 30 TeV) is a vital tool in the study of the non-thermal universe. The interpretation of the observations in this energy region requires the precise modeling of the attenuation of photons due to pair production interactions, where the targets are the radiation fields present in interstellar space. For gamma rays with energy E > 300 TeV the attenuation is mostly due to the photons of the Cosmic Microwave Background Radiation (CMBR). At lower energy the most important target are infrared photons with wavelengths in the range 50-500 micron emitted by dust. The evaluation of the attenuation requires a good knowledge of the density, and energy and angular distributions of the target photons for all positions in the Galaxy. In this work we discuss a simple model for the infrared radiation that depends on only few parameters associated to the space and temperature distributions of the emitting dust. The model allows to compute with good accuracy the effects of absorption for any space and energy distribution of the diffuse Galactic gamma ray emission. The absorption probability due to the Galactic infrared radiation is maximum for E around 150 TeV, and can be as large as P_abs around 0.45 for distant sources on lines of sight that pass close to the Galactic Center. The systematic uncertainties on the absorption probability are estimated as Delta P_abs < 0.08.

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