摘要
介绍了天体物理过程中的甚高能γ射线(TeV能段)的发射机制、探测方法和甚高能γ射线天文学对于宇宙线和天体物理学研究的意义。还简要概述了国内外的甚高能γ天文学探测实验以及所取得的物理成果。
A brief review about the basic ideas and current status, especially the recent high- lights, of the very high energy （VHE, ≥ TeV） γ-ray astronomy is given here. It is known that the emission mechanisms of VHE γ-rays in astronomical environment are generally of two types： hadronic induced and leptonic induced. In the former case γ-rays are generated through the decay of π0 mesons generated by collisions of cosmic ray （CR） nuclei and ambient medium. While in the latter one γ-rays are usually produced due to Inverse Compton scatterings of CR electrons off background photons and the bremsstrahlung radiation when electrons propagate in the medium. Therefore VHE γ-rays are directly connected with the origin and interaction of high energy CRs, and are thought to be an important tool to unveil the fundamental questions of CR physics and astrophysics. Since the flux of γ-rays drops rapidly with the increase of energy, the detection of VHE γ-rays is out of the reach of satellites and needs to be performed using the ground-based large area detectors. VHE γ-ray photons will induce electromagnetic cascades （namely, extensive air shower, EAS） when propagating in the atmosphere. The cascade secondaries are recorded and used to derive the information of the incident γ-rays. Usually there are two detection techniques. One is to directly detect the EAS secondary particles using detector arrays, and the other is to record the Cherenkov light generated by cascade secondaries when going through the air using telescopes. There are more than ten VHE γ-ray observatories are in operation at present in the world. Based on these experiments, especially the Cherenkov telescope arrays, great progress has been achieved in recent years. A new sky, the VHE γ-ray sky, is opened for us to explore the universe. After the first discovery of VHE γ-rays from Crab nebula by Cherenkov telescope Whipple about 20 years ago, there are more than 70 VHE sources are observed with VHE γ-ray emission. Among these sources -30 are identified to be Galactic sources including supernova remnants （SNR）, pulsar wind nebulae （PWN）, X-ray binaries and so on. There are also some sources are possibly connected with the molecular clouds and open clusters. About 20 sources are extragalactic ones, which are mostly blazar-like active galactic nuclei （AGN）. The detection of these VHE γ-ray sources plays a very important role in searching for the origin and understanding the acceleration of CRs. There are another - 20 sources are unidentified ones （＂dark＂ sources）, which attract great attention of people due to the mysterious natures. These ＂dark＂ sources are possibly connected with new physics. Finally the situation of VHE γ-ray study in China is introduced. The two CR observatories in China, Tibet-AS7 and ARGO-YBJ, are also dedicated to make contribution to the VHE γ-rays field. The pervious achievements, current status and future prospects of Tiber-ASγ and ARGO-YBJ are peresented.
出处
《天文学进展》
CSCD
北大核心
2009年第1期47-57,共11页
Progress In Astronomy
基金
国家自然科学基金资助项目(10575111
10773011)
中国科学院高能物理研究所粒子天体物理中心重点实验室开放课题资助项目
关键词
高能天体物理学
甚高能γ射线
宇宙线
high energy astrophysics
very high energy γ-rays
cosmic rays
