Point Sources of TEV and PEV Cosmic Gamma Rays

Abstract

The study of PEV gamma ray sources seems to be the best method to search for the origin of high energy cosmic ray nuclei. Detection of TeV and PeV gamma ray sources is the only method which combined with other observations, such as anisotropy measurements, can answer the question whether the ultra high energy cosmic ray particles are accelerated in point sources, or on large scales. The two major experimental methods used for observing and measuring very high energy cosmic gamma rays, the atmospheric Cerenkov technique and the extensive air shower technique are reviewed. With the rapid development of very high energy gamma ray astronomy a relatively large number of TeV and PeV gamma ray sources has been observed using the above techniques, but only one TeV source, the Crab Nebula is completely well confirmed, and is the best candidate for the standard candle of TeV gamma ray astronomy. Observations of other potential TeV and PeV gamma ray point sources are presented, and some of the major questions of very high energy gamma ray astronomy and astrophysics are discussed.