Institute for Advanced Study Astrophysics Seminar

The Galactic satellite dSph galaxies are the most dark matter dominated, the smallest, and the lowest luminosity galaxies known. They may well be the first bound objects. Recently we have discovered many, and quantified their structure, and internal mass distributions. Surprising results include an apparent minimum luminosity spatial size for all galaxies -100pc-, apparently cored dark matter distributions, and uniformly low central mass densities - 10GeV/cc. None of these properties is as predicted in standard CDM galaxy formation models, while all challenge some types of particle proposed to dominate CDM.