LARGE SCALE NUMERICAL SIMULATIONS ON THE FORMATION OF DISK GASAXIES AND THE ORIGIN OF THE HUBBLE SEQUENCE

对在宇宙学数值模拟中形成的盘状星系的形成过程进行了研究。特别注意了矮星系的动力学演化，这些矮星系是由已经形成的宿主星系组成的。在吸积之后，这些矮星已经被宿主星系的潮汐力完全摧毁，并形成了它的晕的一部分。对这些被摧毁的矮星系的恒星运动学分析表明，它们产生的晕星虽然失去了空间特性，但仍能记住其祖先矮星系的运动学并保持其特征速度;另一个高分辨率数值模拟研究了吸积矮星系对宿主星系盘的引力效应。我们发现，一个质量为2 x 10^太阳质量的矮星系<10>，从银河系中心经过15 kpc时，应该会在银盘中产生一个大的翘曲。这一结果可以定性地解释观测到的高速中性氢云（复合体C）的分布。然而，没有观测到具有所需轨道的矮星系，这表明复合体C不太可能以这种方式形成。同时，还发现上述矮星系的吸积导致了银盘的潮汐破裂，说明银盘形成后不应该发生吸积作用。对小麦哲伦云（SMC）的演化进行了个案研究。通过对气体和恒星成分以及星星形成过程的一致模拟表明，SMC中中性氢的分布和年轻恒星的存在可以解释为SMC与大麦哲伦云和银河系相互作用的结果。

Formation process was investigated of the disk galaxies formed in the cosmological nu-merical simulation. Special attention was paid to the dynamical evolution of dwarf galaxies which acereted to the already formed host galaxies. After accretion, these dwarfs have been destroyed completely by the tidal force of the host galaxy, and formed a part of its halo. Stellar kinematical analysis of these destroyed dwarf galaxies revealed that the halo stars they produced memorize the kinematics of their progenitor dwarfs and maintain their characteristic velocity, although these stars lose spatial identity.A separate high resolution numerical simulation investigated the gravitational effects which accreting dwarfs extert on the disk of the host galaxy. It was found that a dwarf galaxy with a mass of 2 x 10^<10> solar masses passing 15 kpc from the center of our Galaxy should produce a large warp in the galactic disk. This result can explain qualitatively the observed distribution of a high-velocity neutral hydrogen cloud (Complex C). However, no dwarf galaxy is observed which has the required oribit, indicating that the Complex C is unlikely to have formed in this way. It was also found that the accretion of the above dwarf galaxy leads to the tidal disruption of the galactic disk, suggesting that no such accretion should have occurred after the galactic disks have formed.A case study was carried out on the evolution of the Small Magellanic Cloud (SMC), which is one of the accreting dwarfs of our Galaxy. A consistent simulation of the gaseous and stellar components and the star formation process has revealed that the observed distribution of the neutral hydrogen and the existence of young stars in the SMC can be explained as a result of the interaction between the SMC and the Large Magellanic Cloud and our Galaxy.