- Broida 1640
Carlos Frenk - Durham University
The LCDM cosmological model accounts surprisingly well for an impressive array of data on the large-scale structure of the universe, from scales of a few megaparsecs to a few gigaparsecs. On submegaparsec scales, however, the model cannot be tested with the same degree of rigour as on larger scales where microwave background radiation data and measures of galaxy clustering provide clean and well-understood diagnostics. Yet, it is precisely on these small scales that the nature of the dark matter manifests itself most clearly. Satellite galaxies, like those that orbit the Milky Way, are a particularly informative population. The LCDM model makes quite definitive predictions for the properties of this population and recent kinematical data indicate that the internal structure of the satellites may not be what the simplest version of the theory predicts. I will discuss possible solutions to this discrepancy, ranging from exotic baryonic processes that could alter the structure of subhalos to the more radical assumption that the dark matter is not what the standard theory assumes.