The Dragonfly Project: Imaging the outer limits of nearby galaxies

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Simulations of galaxy formation generically predict that all luminous galaxies are embedded in extensive tidal debris fields, caused by occasional major mergers and the continuous accretion of small satellite galaxies. These debris fields are curiously missing around actual galaxies. While this may indicate that revisions to the standard cosmology are needed, a more mundane explanation is that we have not yet obtained sufficiently deep observations to detect the debris fields. This award provides support for the Dragonfly Project that will attempt such a detection. The project is an ultra low surface brightness imaging survey with the Dragonfly telescope of all luminous galaxies within a distance of 30 megaparsecs (Mpc) that are visible from New Mexico. Over the award period of 3 years, the investigators will obtain 40 hr deep images of a complete sample of 72 luminous nearby galaxies.Recent simulations suggest that the debris mostly lives at surface brightnesses of 29 to 31 mag per arcsec^2, fainter than the typical deep imaging limit of about 28 mag per arcsec^2. The investigators have constructed a telescope for the specific purpose of determining whether all galaxies have ultra low surface brightness tidal debris around them on scales of 30--100 kpc. The collected data will reach about 30 mag per arcsec^2 on 3 arcsec scales. The Dragonfly telescope is an array of telephoto lenses coupled with standard charge-coupled device (CCD) imagers. The latest generation of these lenses has nano-fabricated coatings that minimize scattered and reflected light. Together, these lenses constitute a perfectly baffled telescope with extremely fast, all-refractive optics and better scattered light control (by an order of magnitude) than existing reflecting telescopes.The investigating team will make the fully processed and calibrated images publicly available through a web interface. The project integrates education and research in the following ways: (1) The project is complementary to multi-year instrumentation efforts on large telescopes and is well-suited for graduate student training in astrophysical instrumentation. (2) The straightforward remote operation model lends itself well to classroom teaching and demonstrations. The telescope will be integrated into the undergraduate and graduate curriculum at Yale University and will also be used as a science demonstration tool for high school students.