Date of Award
Doctor of Philosophy
Physics and Astronomy
An investigation into the causes of star formation in tidal tails has been conducted using a restricted three-body dynamical model in conjunction with a broad-band photometric evolutionary code. In these models, regions of compression form inside the disk and along the tidal tail and tidal bridge;The effects these density changes have on the colors of the tidal features are examined with a broad-band photometric evolutionary code. A spiral galaxy population is synthesized and the effects of modest changes in the star formation rate are explored. Limits on the density changes needed to make detectable changes in the colors are calculated using a Schmidt (1959) Law;These models suggest that the blue colors and knotty features observed in the tidal features of some galaxies result from increased rates of star formation induced by tidally produced density increases. Limitations of this model are discussed along with photometric evolutionary models based on the density evolution in the tails;The Lynds and Toomre (1976) interpretation of ring galaxies as the natural result of a nearly head-on collision between a disk galaxy and a companion galaxy has become widely accepted. Similarly, Quinn's (1984) interpretation of the shells in elliptical galaxies as the aftermath of the cannibalization of a low-mass companion has been quite successful in accounting for the observations. Restricted three-body calculations of high inclination, low impact parameter encounters demonstrate that the shell-like ripples observed in a number of disk galaxies (cf. Schweizer and Seitzer 1988) can also be produced as collisional artifacts from internal oscillations much as in ring galaxies. However, in this case it is assumed that the target is an early-type disk with a sufficiently low gas fraction that recent star formation does not dominate the appearance of the disturbed disk. It should be emphasized that the models presented here are in a transient stage of an evolutionary sequence, whose outcome is most probably merger along the lines suggested by previous models of shells (Quinn 1988);References. Lynds, R. and Toomre, A. (1976) Ap. J. 209, 382. Quinn, P. (1984) Ap. J. 274, 596. Schmidt, M. (1959) Ap. J. 129, 243. Schweizer, F., and Seitzer, P. (1988) Ap. J. 328, 88.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
John F. Wallin
Wallin, John F., "Dynamic and photometric evolutionary models of tidal tails and ripples " (1989). Retrospective Theses and Dissertations. 9095.