Quasars, High-resolution Spectra In The Ly¦Á Forest Evolution

In the past several decades, we got a all-around view about the nature of Lyman-alpha (Lya) forest. First, the large number of absorption lines primarily dueto Lya absorption by intervening neutral hydrogen along the line of sight to the QSO. Second, the evolution of the number density of these ilnes can be described by a power law in 1+z with index . Nowadays, the researchs about QSO are mostlybased on moderate-resolution spectra (1 -2 A) or lower resolution spectra. There are evidently disadvantages in researchs of QSOs using the moderate-resolution spectra and the low-resolution spectra. A large number of absorption lines are gathering in thespectra region where the wave length is shorter than 1216(1 + zem), and the mixture of the lines is very serious. High-resolution spectra contains more information, so it is necessary to study Lya forest with high-resolution spectra.The main purpose of this thesis is to study the evolution of Lya forest by usinghigh-resolution QSO spectra. A larger sumple is formed by 19 high-resolution QSO spectra obtained from literature. By calculation based on the sumple we obtained thevalue of Y and study the evolution of Lya forest. And we study the relationship of the evolution with redshift and the threshold of equivalent width.