Imaging the Outskirts of Nearby Disk Galaxies

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Precisely how galaxies initially form and how they change throughout their lifetime are among the least understood problems in astrophysics. Many projects are centered on unraveling these mysteries. This project relies on the outskirts of galaxy disks to provide clues about the dynamical evolution of their host galaxy. In galaxy outskirts are preserved the dynamical signatures of past accretions and evolutionary processes such as radial migration, accretion, star formation thresholds, and low level in situ star formation. The principal investigator plans to obtain deep, wide-field images of nearby disk galaxies within 4--10 Mpc to study the structure, stellar populations, and star forming properties of their outer disks. The combination of the investigators' experience with deep, very low surface brightness measurements and the unique telescope/detector instrumentation are ideally suited toward this project. The primary scientific motivations are (1) to determine the structure of extended galaxy disks, (2) to determine how much star formation has contributed to the growth of outer disks, (3) to determine how accretion shaped nearby galaxies, and (4) to determine how surface photometry and discrete star counts compare in their ability to probe the outskirts of galaxies.Educationally, this project will provide opportunities for beginning students to get hands-on research observatory experience---as an observer and as an instrumentalist. Such training is critical for students and for an astronomical community that needs technically-trained scientists. The principal investigator will continue his excellent history of providing his imaging and simulations to planetarium shows and to public outreach web sites, and he will give public talks at local astronomy clubs and the Cleveland Museum of Natural History.