Program: GN-2006A-Q-28

GALEX has discovered a population of spiral galaxies hosting extended UV ("XUV") disks dramatically larger than their optical extent. Such galaxies support star-formation at an unexpectedly high rate in locales previously thought to be dynamically stable. Indeed, XUV disks are populated with UV-bright stellar complexes categorically lacking bright, counterpart HII regions. We propose GMOS-N observations of PGC9103, one of the most extreme XUV disks known. Deep broadband/H-alpha imaging will permit photometric determination of cluster mass, age, and extinction, while ensuring a complete census of HII regions. Multi-object spectroscopy will allow us to measure nebular abundances and density throughout PGC9103's XUV disk. We intend to reassess the star formation law and gauge the importance of XUV disks relative to galaxy evolution.