Abstract:

Astronomers and cosmologists live in interesting times. According to the standard cosmological model, cold dark matter appears to dominate the dynamics of structure, and yet it is unclear whether it can reproduce the properties of galaxies and clusters at smaller scales. The geometry and dynamics of the universe have been measured to unprecedented precision, and yet most of the energy of the universe is in the form of an unexplained dark energy. I present new observational tests of the standard cosmological model. In particular, I focus on the following questions: are there universal dark matter profiles? Is there dark matter substructure? What is the equation of state of dark energy? I discuss the results, and underscore the crucial need to understand the interplay between baryons and dark matter as part of the paradigm. I conclude by discussing future prospects.