Probing the Low Surface Brightness Universe with the World's Largest Refractor: the Metre-Class Dragonfly Telephoto Array

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The University of Toronto and Yale have developed a novel new telescope, the Dragonfly Telephoto Array, which is designed to probe the composition of the Universe at very low surface brightness levels. This is an area of astronomy that is almost totally unexplored, and in the last 18 months we have used this telescope (constructed from an array of 10 high-end commercial telephoto lenses) to probe the Universe down to hitherto impossibly faint surface brightness levels. A number of interesting discoveries have been made, including the existence of a new population of giant but faint galaxies that preferentially inhabit rich galaxy clusters. These "ultra diffuse galaxies" are as big as the Milky Way galaxy but 1/100 of its mass, and explaining how they survive in the very hostile environment of a galaxy cluster is a major puzzle. These results are only the tip of the iceberg. It is now clear that the low surface brightness Universe is a treasure trove of almost unexplored astrophysical phenomena, ranging from giant dust rings around planets in our Solar system, to supernova light echoes, to high velocity clouds raining onto the disk of the Milky Way, to intra-group and intra-cluster light and even to new emission mechanisms in rich clusters of galaxies. The race is now on to study these, but a major limiting factor is the small size of the Dragonfly Telephoto Array, which currently requires extremely long exposure times to get down to ultra-faint surface brightness levels. We have therefore devised a plan to increase the size of the array by a factor of six. In this proposal we seek the funds needed for the final component of the upgraded telescope - two large equatorial mounts that will support 58 telephoto lenses we have already secured. When completed, the upgraded Dragonfly Telephoto Array will be the world's largest refracting telescope.