Campus, Varian 355
The abundance of low mass halos provides a fundamental constraint of the nature of dark matter via the free-streaming length. Models with GeV scale dark matter (Cold Dark Matter) match observations of structure remarkably well for mass scales above that of the Milky Way. At lower masses, such comparisons become more difficult as galaxies become fainter, and theoretical predictions for how galaxies form become more uncertain. My work involves two complementary approaches to measuring the abundance of small scale structure. First I discuss my measurements of the luminosity function of satellite galaxies across more than half the age of the Universe and in a variety of environments, and demonstrate how these measurements provide a deeper understanding of the physics of star formation in low mass dark matter halos. I will also present my novel approach to strong gravitational lensing which makes it possible to detect a much larger number of low mass dark matter halos independently of baryon content. I will conclude by discussing future prospects for these programs given the next generation of ground and space based facilities.