  Spitzer IRAC observations of two fields in the XUV-disk of M83 have been
recently obtained,3R_{HII} away from the center of the galaxy (R_{HII)=6.6
kpc).GALEX UV images have shown the two fields to host in-situ recent star
formation.The IRAC images are used in conjunction with GALEX data and new HI
imaging from THINGS to constrain stellar masses and ages of the UV clumps in
the fields,and to relate the local recent star formation to the reservoir of
available gas. multi wavelength photometry in the UV and mid-IR bands of 136 UV
clumps(spatial resolution >220pc) identified in the two target fields, together
with model fitting of the stellar UV-MIR SED,suggest that the clumps cover a
range of ages between a few Myr and >1Gyr with a median value around
<100Myr,and have masses in the range 10^3-3*10^6M, with a peak ~10^4.7M.The
range of observed ages,for which only a small fraction of the mass in stars
appears to have formed in the past ~10Myr, agrees with the dearth of Ha
emission observed in these outer fiel ds. At the location of our IRAC fields,
the HI map shows localized enhancement and clumping of atomic gas. A comparison
of the observed star formation with the gas reservoir shows that the UV clumps
follow the Schmidt--Kennicutt scaling law of star formation,and that star
formation is occurring in regions with gas dens ities at approximately (within
a factor of a few) the critical density value de -rived according to the Toomre
Q gravitational stability criterion. The signifi cant 8 micron excess in
several of the clumps (16% of the total by number accou nting for ~67% of the 8
micron flux)) provides evidence for the existence of dust in these remote
fields, in agreement with results for other galaxies. Furt hermore, we observe
a relatively small excess of emission at 4.5 micron in the clumps...
