The Universal Initial Mass Function In The XUV Disk of M83
  We report deep Subaru Halpha observations of the XUV disk of M83. These new
observations enable the first complete census of very young stellar clusters
over the entire XUV disk. Combining Subaru and GALEX data with a stellar
population synthesis model, we find that (1) the standard, but
stochastically-sampled, initial mass function (IMF) is preferred over the
truncated IMF, because there are low mass stellar clusters (10^{2-3}Msun) that
host massive O-type stars; that (2) the standard Salpeter IMF and a simple
aging effect explain the counts of FUV-bright and Halpha-bright clusters with
masses >10^3Msun; and that (3) the Halpha to FUV flux ratio over the XUV disk
supports the standard IMF. The Subaru Prime Focus Camera (Suprime-Cam) covers a
large area even outside the XUV disk -- far beyond the detection limit of the
HI gas. This enables us to statistically separate the stellar clusters in the
disk from background contamination. The new data, model, and previous
spectroscopic studies provide overall consistent results with respect to the
internal dust extinction (Av~0.1 mag) and low metallicity (~0.2Zsun) using the
dust extinction curve of SMC.
