How have elliptical and spiral galaxies developed differently through interactions with other galaxies?

Question

What will be an ideal response?

Answer 1

Elliptical galaxies are usually found in rich clusters with many galaxies, and most of the galaxies in these clusters are elliptical. Collisions in a rich cluster will collide and interact often, and this must mean that ellipticals have been through collisions in their lifetimes.Collisions trigger bursts of star formation which consumes gas and dust. Ellipticals do not contain much gas and dust because star formation triggered by collisions and mergers have used up all of the available gas.The random stellar orbits found in ellipticals would not be disrupted through collisions and mergers.Spiral galaxies are found in poor clusters where collisions are rare. The disk of a spiral galaxy would be disrupted and destroyed in a collision with another large galaxy. Spirals contain large amounts of gas and dust that would be used up in a starburst triggered by a collision with another galaxy. Spiral galaxies can not have had collisions with other large galaxies.Interactions between spirals and smaller galaxies appear to be important in maintaining structures like spiral arms and bars.