Characterizing Cosmic-Ray Propagation in Massive Star-Forming Regions:
  The Case of 30 Doradus and the Large Magellanic Cloud
  Using infrared, radio, and gamma-ray data,we investigate the propagation
characteristics of cosmic-ray (CR) electrons and nuclei in the 30 Doradus
(30\,Dor) star-forming region in the Large Magellanic Cloud (LMC) using a
phenomenological model based on the radio-far-infrared correlation within
galaxies. Employing a correlation analysis, we derive an average propagation
length of \sim 100-140 pc for \sim 3 GeV CR electrons resident in 30 Dor from
consideration of the radio and infrared data. Assuming that the observed
gamma-ray emission towards 30 Dor is associated with the star-forming region,
and applying the same methodology to the infrared and gamma-ray data, we
estimate a \sim 20 GeV propagation length of 200-320 pc for the CR nuclei. This
is approximately twice as large as for\sim 3 GeV CR electrons, corresponding to
a spatial diffusion coefficient that is \sim 4 times higher, scaling as
(R/GV)^{\delta} with \delta \approx 0.7-0.8 depending on the smearing kernel
used in the correlation analysis. This value is in agreement with the results
found by extending the correlation analysis to include \sim 70 GeV CR nuclei
traced by the 3-10 GeV gamma-ray data (\delta \approx 0.66+/-0.23). Using the
mean age of the stellar populations in 30 Dor and the results from our
correlation analysis, we estimate a diffusion coefficient D_{R} \approx 0.9-1.0
\times10^27 (R/GV)^{0.7} cm^2 s^-1. We compare the values of the CR electron
propagation length and surface brightness for 30 Dor and the LMC as a whole
with those of entire disk galaxies. We find that the trend of decreasing
average CR propagation distance with increasing disk-averaged star formation
activity holds for the LMC, and extends down to single star-forming regions, at
least for the case of 30 Dor.
