CHANGE OF MASS DISTRIBUTION IN ENCOUNTERS

摘要

Encounters of protostars surrounded by accretion discs are thought to be quite likely events in high density star-forming regions. Characteristic for encounters of disc-surrounded protostars is the appearance spiral patterns and long-term development of an elliptical or ring structure. Star-disc as well as disc disc encounters will be investigated in detail. It is shown that the appearance of superkeplerian velocities in the tidal tail is a key feature which can be used to predict properties such as spiral arm strength, rings and elliptic discs. Further simulation results show that there are two different mechanisms at work to create the first two spiral arms - the first spiral arm resembles a shock-like structure, whereas the second arm ( and possibly subsequent arms) is caused by a relative movement between the central star and the center of mass of the disc, caused by the mass imbalance in the disc.