Astronomy Colloquium

The talk will describe a new telescope concept, optimized for low surface brightness imaging. The Dragonfly Telephoto Array consists of 48 high-end telephoto lenses, creating the equivalent of an f/0.4 refractor with a 1m aperture. Early results from Dragonfly include a measurement of the stellar halos around nearby spiral galaxies down to ~32 mag/arcsec^2 and the identification of new satellite galaxies. Perhaps the most unexpected result so far is the discovery of a population of Milky Way-sized, very low surface brightness galaxies in rich clusters. Follow-up HST imaging and extremely deep Keck spectroscopy of two of these "Ultra Diffuse Galaxies" show that they are massive and dark matter dominated, and have large numbers of globular clusters.