|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 2000 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1999 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1998 : ¥1,700,000 (Direct Cost : ¥1,700,000)
I investigated formation and evolution of small galaxies, satellites and dwarf galaxies, in the framework of the Cold Dark Matter Universe. According to computer simulations of the structure formation in the CDM universe, it is suggested that many satellite galaxies are formed surrounding a host galaxy. Although the number of satellites is large, since their total mass is very much smaller than that of the host galaxy, they have little effect on the formation and evolution of the host galaxy. The most of satellites are likely to be absorbed by the host galaxy. If a satellite survives and retains the gas, it evolves forming stars and will be observed as a dwarf galaxy. The gas ejection is significant for galaxies with mass small than a billion solar masses. For normal star formation rate, UV heating in early phase of galaxy formation is main cause of gas ejection ; when a clump of dark matter turns around and collapses, the increased pressure caused bv UV heating prevents the gas to collapse and eventually lost from the galaxy. Galaxies with mass larger than a billion solar masses hardly lose their gas, but if they lose the gas, it will be caused by violent star formation, interactions with host galaxies or ram pressure of intergalactic matter, If a satellite galaxy passes through the gas disk of host galaxy, significant fraction of the gas will be stripped away and subsequent star formation is suppressed. As a result, very faint dark galaxy is formed mainly composed of dark matter with very little stars.