Star streams: bump hunting in the Milky Way halo

How do galaxies form?

“Bottom-up” formation

Observations of real galaxies

"Do galaxies form in a..."

Physics of satellite destruction

"Collisionless Boltzmann equation:"

Early evidence of substructure:
one velocity dimension:

Introducing our nearest neighbor:
the Sagittarius dwarf galaxy

Tidally disrupting

Star stream detected in two spatial dimensions

Sagittarius and its star streams

Satellite streams seen against smooth background -- simulations

The future: six dimensions

The Spaghetti Survey

“Pencil-beam” survey

How to test for substructure?

Simulated stream

Observational realities

Test with simulations

Simulations

Cluster analysis

Our sample in 4-D

Summary