Exploring the Far Distant Universe by Using Quasars as a Probe

利用类星体吸收谱线系统的III柱密度分布和数密度演化规律等观测资料，研究了年轻星系的演化特征和z = 0.3 ~ 4红移处的漫射紫外通量。在这个研究项目中，我集中研究了以下两类：(1)作为星系晕探测的CIV吸收线系统；(2)作为星系间云探测的三种HI吸收系统。主要结论如下。对于第一类，我利用观测资料研究了气体晕的动力学行为、重元素丰度的增加速率和漫射紫外线通量的时间变化。因此，我得出结论，在z = 3到2的红移期间，gaecous晕迅速膨胀，重元素丰度迅速增加。另一方面，我发现漫射紫外线通量在这个时期是恒定的。这些结论表明，年轻星系在恒星形成过程中更活跃，由于恒星强烈的能量喷射，气体晕动态膨胀到100 kpc。同时，来自星系的紫外线的发射在很大程度上促成了漫射紫外线背景。对于第二类，我提出了三种III吸收系统的统一模型，即Lyman α森林系统、Lyman极限系统和阻尼Lyman α线系统。基本模型是一个微晕，它是一个被冷暗物质引力限制的星系间云。这个微光晕被电离并被漫射的紫外线流加热。因此，如果扩散紫外通量随时间变化，则驱动微晕的演变。在微晕的包层中，气体被高度电离，它被探测到为莱曼α森林。在中心部分，紫外线通量减弱，气体保持中性。这个区域被观察为莱曼极限系统或阻尼莱曼α线系统。巨大的小光晕将坍缩并演化成星系，这是第一类的吸收系统。因此，我得出结论，整个吸收线系统是在冷暗物质主导的宇宙下再现的。少

By utilizing the observational data such as III column density distribution and number density evolution laws of absorption line systems of quasars, I investigated the evolutionary features of young galaxies and diffuse UV flux at the red shifts of z = 0.3 - 4. In this research project, I concentrated to the following two categories : (1) CIV absorption line systems as a probe of galactic halos, and (2) three kinds of HI absorption systems as a probe of intergalactic clouds. Main conclusions are as follows.As for the first category, I studied the dynamical behavior of a gasecous halo, the increasing rate of heavy element abundances and the time variation of diffuse UV flux utilizing the observational data. As a result, I concluded that the gaecous halo is rapidly expanding and the heavy element abundances are increasing fast during the red shift z = 3 to 2. On the other hand, I found the diffuse UV flux to be constant in this epoch. These conclusions indicate that young galaxies were s … More o active in star formation and gaseous halos dynamically expand to 100 kpc due to the intense energy ejection from stars. At the same time, the emission of UV light from galaxies largely contributes to the diffuse UV background.As for the second category, I proposed a unified model for three kinds of III absorption systems, which are the Lyman alpha forest, Lyman limit systems and damped Lyman alpha line systems. The fundamental model is a minihalo which is an intergalactic cloud confined by the gravity of cold dark matter. This minihalo is ionized and heated up by the diffuse UV flux. Therefore, if the diffuse UV flux varies in time the evolution of minihalos is driven. In the envelope of a minihalo the gas is highly ionized and it is detected as the Lyman alpha forest. In the central part the UV flux is attenuated and the gas keeps in neutral. This region is observed as an Lyman limit system or damped Lyman alpha line system. Massive minihalos will collapse and evolve to galaxies, which are detected as the absorption systems of the first category.Accordingly, I concluded that the whole absorption line systems are reproduced under the cold dark matter dominated universe. Less