  Galaxy formation simulations demonstrate that cosmic-ray (CR) feedback may be
important in the launching of galactic-scale winds. CR protons dominate the
bulk of the CR population, yet most observational constraints of CR feedback
come from synchrotron emission of CR electrons. In this paper, we present an
analysis of 105 months of Fermi Gamma-ray Space Telescope observations of the
Small Magellanic Cloud (SMC), with the aim of exploring CR feedback and
transport in an external galaxy. We produce maps of the 2-300 GeV emission and
detect statistically significant, extended emission along the Bar and the Wing,
where active star formation is occurring. Gamma-ray emission is not detected
above 13 GeV, and we set stringent upper-limits on the flux above this energy.
We find the best fit to the gamma-ray spectrum is a single-component model with
a power-law of index $\Gamma=-2.11\pm0.06\pm0.06$ and an exponential cutoff
energy of $E_{\rm c} =13.1\pm5.1\pm1.6$ GeV. We assess the relative
contribution of pulsars and CRs to the emission, and we find that pulsars may
produce up to 14$^{+4}_{-2}$% of the flux above 100 MeV. Thus, we attribute
most of the gamma-ray emission (based on its spectrum and morphology) to CR
interactions with the ISM. We show that the gamma-ray emissivity of the SMC is
five times smaller than that of the Milky Way and that the SMC is far below the
calorimetric limit, where all CR protons experience pion losses. We interpret
these findings as evidence that CRs are escaping the SMC via advection and
diffusion.
