Frontier of Energy and Distance of Very High Energy Gamma-Ray Astronomy

甚高能伽马射线天文学的能量与距离前沿

基本信息

批准号：
15540263
负责人：
KIFUNE Tadashi
金额：
$ 1.73万
依托单位：
Shinshu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540263/
关键词：
Very High Energy Gamma Ray Astronomy Non-thermal Phenomena in the Universe Particle Acceleration Origin of Cosmic Rays Pari production of Electron and Positron Cosmic Background Radiation Sources of Very High Energy Gamma Rays Imaging Atmosp

项目摘要

Very energetic gamma rays collide with universal cosmic background radiation of microwave and infrared band to create pairs of electron and positrons, thus initiating a cascade process of creating a number of electrons and gamma rays in the extragalactic space. The effect of absorption and regeneration of gamma-rays which are radiated from far distant sources was calculated, in order to draw a view in near future of TeV Gamma Ray Astronomy and to study ultra high energy phenomena in the Universe.Regeneration of secondary gamma rays causes accumulation of gamma ray flux in the energy region around 10-100 TeV. However, the increasing factor of the flux is at most about 3 when energy spectrum of primary gamma rays is as hard as the power index alpha of -2, while the factor is less than 10% for in the case of alpha equal to 2.5. On the other hand, more prominent effect of the cosmic cascade can be caused by electrons, the secondary product of the cascade process, of energies higher than 10^{15} eV,. Such high energy electrons radiate synchrotron photons, of which energy would be into the lower energy band as high as GeV gamma rays, possibly to provide evidence of extremely high energy gamma rays. However, the process depends on the strength of magnetic field in the extragalactic space. Thus, there remain investigations to be done in more details. Another interesting feature which may appear is a spectral break in the energy spectrum of electrons, due to the transition from the Thomson scattering to Compton scattering in the collision of electrons with photons of the background radiation.The cascade process causes a considerable angular spread of incident gamma-rays, and the telescope with a wide field of view is expected to increase importance, as very high energy gamma ray astronomy extends into higher energy region and far distances.

高能伽马射线与微波和红外波段的宇宙背景辐射碰撞，产生电子和正电子对，从而启动在河外空间产生大量电子和伽马射线的级联过程。计算远距离源辐射的伽马射线的吸收和再生效应，以绘制TeV伽马射线天文学的近期视图，研究宇宙中的超高能现象。次级伽马射线的再生导致 10-100 TeV 能量区域内伽马射线通量的累积。但当初级伽马射线能谱较硬，功率指数α为-2时，通量增加系数最多为3左右，而当α等于2.5时，通量增加系数小于10％。另一方面，更显着的宇宙级联效应可能是由级联过程的次级产物、能量高于10^{15} eV的电子引起的。这种高能电子辐射出同步加速器光子，其能量将进入高达GeV伽马射线的较低能带，这可能提供极高能量伽马射线的证据。然而，这个过程取决于河外空间的磁场强度。因此，仍有待进行更详细的调查。可能出现的另一个有趣的特征是电子能谱中的光谱断裂，这是由于电子与背景辐射的光子碰撞时从汤姆逊散射到康普顿散射的转变。级联过程导致入射角相当大随着极高能伽马射线天文学扩展到更高能量区域和更远的距离，伽马射线和宽视场望远镜的重要性预计将增加。