Searching For VHE Gamma-ray Point Sources With The Data From Tibet Ⅲ Array

Cosmic rays are high-energy particles, coming from the astrospace. Analyzing the cosmic rays is one of the most important ways to get the information of the celestial badies. Cosmic ray physics is a discipline that mainly studies the origin,acceleration, propagation and modulation of the cosmic rays. And the generation mechanism of the cosmic rays is always the basic question of the cosmic ray physics. Gamma ray, one kind of the neutral high-energy particles, become extraordinary important because it was not modulated by the Magnetic field among their arrival, and so carried the information of the direction and some other physical characteristics of the source. Even it is less than 1% in the primary particles.The observation on high-energy gamma-ray mainly includes experiment based on the satellites or balloon high in the air , Air Cherenkov Telescope experiments and Extensive Air Shower(EAS) array etc. Each of them has its own advantages: the first kind of experiment can give direct information on cosmic rays, and the second one has the ability to distinguish showers induced by gamma rays and hadrons, while the last one has the advantages of wide detective angle, good energy resolution and high duty cycle ,etc…The aim of this thesis is to search for the high-energy gamma ray source by using the data obtained from the Tibet III Array of Yangbajing AS γ experiment which was one of the most important experiments in all the same kind. The datas, phase1 to phase5 , from TibetIII Array are used in the work of this thesis. The field of all sky in the declination band between -10°-70° is searched for the very high-energy gamma ray sources with the all-sky scan method. 28 directions with the significance of Gamma-ray signal larger than 4 σ , but none of them exceeds 6 σ . Two point sources, crab and mrk421, among the 87 sources searched have significance 4.41 σ and 5.10 σ respectively.