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Gas dynamics in interacting and merging galaxies

Kevin Mark Olson, University of Massachusetts Amherst


In this dissertation I develop a three dimensional model of the dynamics of gas clouds in interacting galaxies. The gas clouds move under the combined gravitational influence of two galaxies passing close to each other. By performing a multipole expansion of the gravitational field I am able to include the effects of self-gravity within a galaxy. This also allows me to model the case in which the two galaxies merge. The gas clouds are allowed to interact with one another by colliding. They either coalesce to form a larger cloud or are disrupted, depending on their relative kinetic energy as compared to the total gravitational binding energy of the two-cloud system. Various cases are considered in this dissertation by varying such parameters as impact parameter, inclination of the gaseous disk of a galaxy to the orbital plane of the two, interacting galaxies, relative velocity of the galaxies, the mass ratio of the galaxies, and the presence of gas in the second galaxy. As the strength of the interaction increases the more disturbed the interstellar medium becomes. The clouds collide at an increased rate and with larger velocities so that the fraction of collisions which disrupt the clouds rises as the strength of the interaction increases. The region of the galaxy where increased rates of collision are induced also becomes more and more concentrated toward the center of the galaxy. Since interacting galaxies are observed to have elevated star formation rates, I conclude that the star formation induced by the interaction of two galaxies is related to the high velocity, disruptive cloud-cloud collisions. Monitoring the amount of gas mass involved in such collisions allows me to estimate the star formation rate and the luminosity produced by these stars. Considering parameters such as inclination, bound and unbound orbits, the mass of the perturbing galaxy, and the possible presence of gas in both galaxies, I find that the scatter in observations of the infrared luminosity to gas mass ratio can be explained. ^

Subject Area


Recommended Citation

Olson, Kevin Mark, "Gas dynamics in interacting and merging galaxies" (1990). Doctoral Dissertations Available from Proquest. AAI9022730.