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We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 andHolmberg IX. We combine UVOT imaging in three near ultraviolet (NUV) filters(uvw2: 1928 {\AA}, uvm2: 2246 {\AA}, and uvw1: 2600 {\AA}) with ground basedoptical imaging from the Sloan Digital Sky Survey to constrain the stellarpopulations of both galaxies. Our analysis consists of three different methods.First we use the NUV imaging to identify UV star forming knots and then performSED modeling on the UV/optical photometry of these sources. Second, we measuresurface brightness profiles of the disk of M81 in the NUV and optical. Last weuse SED fitting of individual pixels to map the properties of the two galaxies.In agreement with earlier studies we find evidence for a burst in starformation in both galaxies starting ~200 Myr ago coincident with the suggestedtime of an M81-M82 interaction. In line with theories of its origin as a tidaldwarf we find that the luminosity weighted age of Holmberg IX is a few hundredmillion years. Both galaxies are best fit by a Milky Way dust extinction lawwith a prominent 2175 {\AA} bump. In addition, we describe a stacked medianfilter technique for modeling the diffuse background light within a galaxy, anda Markov chain method for cleaning segment maps generated by SExtractor.

Swift UV/Optical Telescope Imaging of Star Forming Regions in M81 and Holmberg IX