What about the Little Guys?

Most galaxy collisions do not involve two big galaxies.

Most collisions involve a larger galaxy swallowing a smaller companion.

In fact, cosmological considerations suggest that most galaxies have experienced a ``minor merger'' in their lifetime.

What then?

Satellite Accretion

• Coupling between orbital and rotational motion can induce bars(Warning: 4.2Mb mpeg) in a disk galaxy.
• Bars can drive gas inflows and starbursts.
• Dynamical stirring heats, thickens, and warps (Warning: 1.8Mb mpeg) the disk. (Kind of like this?)
• Stripping and accretion of companions leads to subpopulations in galaxies.

This is very relevant to our own Milky Way galaxy:

• The Milky Way has several nearby companions.
• The Milky Way is currently ``eating'' the Sagittarius dwarf.
• The Milky Way is a barred galaxy.
• The Milky Way has a ``thick disk'' component.

Previous: Making Ellipticals
Finally: What now?