Hα and UV imaging of Low Surface Brightness Galaxies and Extended UV Disks

GALEX observations have revealed UV emission extending far beyond the optical and H-alpha disks of several nearby spiral galaxies, raising the question of possible massive star deficiency, i.e., deviations from the standard 'universal' stellar initial mass function (IMF) at the upper end, in certain low density environments. We have undertaken an Ha imaging survey of low surface brightness galaxies observed by GALEX and with existing HI maps with the aim of investigating the variation of the H alpha/UV ratio with the local density. Here we present preliminary results for 14 such galaxies observed with the Large Format Camera on the Palomar 200 inch telescope using custom narrow band filters.