Bright Ultraviolet Regions and Star Formation Characteristics in Nearby
  Dwarf Galaxies
  We compare star formation in the inner and outer disks of 11 dwarf Irregular
galaxies (dIm) within 3.6 Mpc. The regions are identified on GALEX near-UV
images, and modeled with UV, optical, and near-IR colors to determine masses
and ages. A few galaxies have made 10^5-10^6 Msun complexes in a starburst
phase, while others have not formed clusters in the last 50 Myrs. The maximum
region mass correlates with the number of regions as expected from the
size-of-sample effect. We find no radial gradients in region masses and ages,
even beyond the realm of Halpha emission, although there is an exponential
decrease in the luminosity density and number density of the regions with
radius. Halpha is apparently lacking in the outer parts only because nebular
emission around massive stars is too faint to see. The outermost regions for
the 5 galaxies with HI data formed at average gas surface densities of 1.9-5.9
Msun/pc2. These low average densities imply either that local gas densities are
high or sub-threshold star formation is possible. The distribution of regions
on a log Mass - log age plot is is usually uniform along log age for equal
intervals of log Mass. This uniformity results from either an individual region
mass that varies as 1/age or a region disruption probability that varies as
1/age. A correlation between fading-corrected surface brightness and age
suggests the former.
