Abstract:

A number of observations of dwarf galaxies pose challenges to our understanding of the clustering of matter on small scales in the current paradigm of structure formation in the Universe—the Lambda-Cold Dark Matter scenario. These include the scarcity of dwarf galaxies compared with the numerous low-mass halos expected in ?CDM (the “missing satellites” problem); the inner mass profiles of cold dark matter halos compared with the rotation curves of dwarf galaxies (the “cusp vs core” problem); the highly anisotropic distribution of satellite galaxies around the Milky Way and Andromeda galaxies (the “satellite alignment” problem); and the low halo masses inferred for the faintest dwarfs (the “too-big-to-fail” problem). I will discuss these challenges, as well as the puzzles and challenges that arise from them and from their possible resolution.