Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Physics and Astronomy

First Advisor

Curtis Struck


This dissertation describes numerical studies of three interacting galaxy systems. First, hydrodynamical models of the collisions in the famous compact galaxy group, Stephan's Quintet, were constructed to investigate the dynamical interaction history and evolution of the intergalactic gas. It has been found that with a sequence of two-at-a-time collisions, most of the major morphological and kinematical features of the group were well reproduced in the models. The models suggest the two long tails extending from NGC 7319 toward NGC 7320c may be formed simultaneously from a strong collisional encounter between the two galaxies, resulting in a thinner and denser inner tail than the outer one. The tails then also run parallel to each other as observed. The model results support the idea that the group-wide shock detected in multi-wavelength observations between NGC 7319 and 7318b and the starburst region north of NGC 7318b are triggered by the current high-speed collision between NGC 7318b and the intergalactic gas. It is expected that other compact groups containing rich extended features like Stephan's Quintet can be modeled in similar ways, and that sequences of two-at-a-time collisions will be the general rule.

The second set of hydrodynamical simulations were performed to model the peculiar galaxy pair, Arp 285. This system possesses a series of star-forming complexes in an unusual tail-like feature extending out perpendicular to the disk of the northern galaxy. Several conceptual ideas for the origin of the tail-like feature were examined. The models suggest that the bridge material falling into the gravitational potential of the northern disk overshoots the disk; as more bridge material streams into the region, compression drives star formation. This work on star-formation in the pile-up region can be extended to the studies of the formation of tidal dwarf galaxies or globular clusters.

Thirdly, the development of spiral waves was studied with numerical models of fast galaxy collisions involving a disk with a high value of the Toomre Q parameter. The models found that spirals slowly developed in the disk do not dissipate in a few outer disk orbital time. The waves in the models persist for a long time, more than 10 outer disk rotation periods, while winding ever tighter. Since fast collisions are common in many galaxy groups and cluster environments, the phenomena and effect presented in the work may be one of the several processes that contribute to galaxy harassment, and a contributor to the Butcher-Oemler effect.


Copyright Owner

Jeong-sun Hwang



Date Available


File Format


File Size

85 pages

Included in

Physics Commons