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I am afraid as I write this 3 weeks later I don't have their names, and I wouldn't have their presentations either anyway. So… to capture the basic information, I did a quick internet search and found the following 2 sources that do an excellent job of capturing the essence of this subject! The first article gives a quick explanation of galactic interaction, and the second provides an animation you can watch in a few seconds instead of a few hundred million years!
High-speed encounters between galaxies will leave the galaxies largely intact, but will result in tidal distortions such as tails and bridges. The Whirlpool Galaxy (M51), for instance, is connected by a tidal bridge of stars to a smaller neighboring galaxy.
Head-on encounters are rarer than glancing encounters. If a small galaxy runs straight through the middle of a large spiral galaxy, a ``tidal wave'' of stars and gas will run outward in the disk of the spiral galaxy. The result is a ring galaxy, in which the most prominent feature is the ring-shaped tidal wave of stars. A famous ring galaxy, known as the Cartwheel Galaxy, is shown at right. The interloping galaxy which passed through the middle of the Cartwheel Galaxy is one of the two galaxies on the right - no one knows which. Note how blue the ring of the Cartwheel Galaxy is; that means it's a site of current star formation, with lots of young O & B main sequence stars.
Low-speed encounters between galaxies result in mergers. Two separate galaxies will join together to form a single elliptical galaxy. The entire merging process takes hundreds of millions of years, so galaxies are seen caught in the act of merging. The two galaxies shown below are known as the ``Antennae'' galaxies. They are in the process of merging with each other; note how tidal forces have warped them into asymmetric shapes. The blue areas within the galaxies are regions where star formation is being triggered.
The Milky Way Galaxy and the Andromeda Galaxy are currently approaching each other at a speed of 300 km/sec. If they are on extremely elongated orbits, they will collide with each other in 3 billion years or so, merging to form a giant elliptical galaxy. (If their orbits are more nearly spherical, they will pass by each other with only minor tidal distortions).
When a large galaxy encounters a smaller one at low speeds, the smaller galaxy is ``cannibalized''. That is, the stars of the small galaxy are incorporated into the larger one, with only a minimal change to the structure of the larger galaxy. The Milky Way Galaxy, it seems, is in the early stages of cannibalizing the Magellanic Clouds.
Astronomy 162: Professor Barbara Ryden
http://www-astronomy.mps.ohio-state.edu/~ryden/ast162_7/notes30.html
In this scientific visualization, two spiral galaxies are set on a collision course. As one slices through the other, both are disrupted. The tidal forces of gravity produce long tails of material streaming away from the collision. The central regions relatively quickly fall together and merge. The visualization is based on research data from a supercomputer simulation, with stars shown in yellow and gas shown blue. Time passes at about 10 million years per second, lasting a total of about 500 million years. Such a collision may occur for our Milky Way Galaxy and the neighboring Andromeda Galaxy in about five billion years.
Visualization by Frank Summers (Space Telescope Science Institute).
Simulation by Chris Mihos (Case Western Reserve University) and Lars Hernquist (Harvard University)
http://oposite.stsci.edu/pubinfo/PR/2002/09/animation.html
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