Swift UV/Optical Telescope Imaging of Star Forming Regions in M81 and
  Holmberg IX
  We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and
Holmberg IX. We combine UVOT imaging in three near ultraviolet (NUV) filters
(uvw2: 1928 {\AA}, uvm2: 2246 {\AA}, and uvw1: 2600 {\AA}) with ground based
optical imaging from the Sloan Digital Sky Survey to constrain the stellar
populations of both galaxies. Our analysis consists of three different methods.
First we use the NUV imaging to identify UV star forming knots and then perform
SED modeling on the UV/optical photometry of these sources. Second, we measure
surface brightness profiles of the disk of M81 in the NUV and optical. Last we
use 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 star
formation in both galaxies starting ~200 Myr ago coincident with the suggested
time of an M81-M82 interaction. In line with theories of its origin as a tidal
dwarf we find that the luminosity weighted age of Holmberg IX is a few hundred
million years. Both galaxies are best fit by a Milky Way dust extinction law
with a prominent 2175 {\AA} bump. In addition, we describe a stacked median
filter technique for modeling the diffuse background light within a galaxy, and
a Markov chain method for cleaning segment maps generated by SExtractor.
