  The galaxies M82, NGC 253, NGC 1068, and NGC 4945 have been detected in
gamma-rays by Fermi. Previously, we developed and tested a model for cosmic ray
interactions in the starburst galaxy M82. Now, we aim to explore the
differences between starburst and active galactic nuclei (AGN) environments by
applying our self-consistent model to the starburst galaxy NGC 253 and the
Seyfert galaxy NGC 1068. Assuming constant cosmic-ray acceleration efficiency
by supernova remnants with Milky-Way parameters, we calculate the cosmic-ray
proton and primary and secondary electron/positron populations, predict the
radio and gamma-ray spectra, and compare with published measurements. We find
that our models easily fits the observed gamma-ray spectrum for NGC 253 while
constraining the cosmic ray source spectral index and acceleration efficiency.
However, we encountered difficultly modeling the observed radio data and
constraining the speed of the galactic wind and the magnetic field strength,
unless the gas mass is less than currently preferred values. Additionally, our
starburst model consistently underestimates the observed gamma-ray flux and
overestimates the radio flux for NGC 1068; these issues would be resolved if
the AGN is the primary source of gamma-rays. We discuss the implications of
these results and make predictions for the neutrino fluxes for both galaxies.
